Thursday, April 26, 2012

Two of the Closest Series Ever

Last night's overtime victory by Washington completed what was likely the closest series in NHL history in terms of score.  Not only was every game decided by a single goal, but 99.4% of the entire series was played with a goal differential of one or less.  The only time either team managed to take a two goal lead over the seven games was when Jay Beagle scored in the second period of game five to put the Caps up 2-0, a margin that lasted less than three minutes before the Bruins cut it to 2-1.

The West had a matchup that was also a strong contender for the title of closest ever right up until the final period of the series.  Phoenix and Chicago went to overtime in each of the first five games of the series, and by the time of the second intermission in game six had spent 99.3% of their series tied or with one of the teams leading by a lone goal.  However, in that final period Phoenix finally broke through and pulled away for a decisive 4-0 win.

I thought it would be interesting to look at numbers broken down by score in these two series to see why they were so tight.

Boston vs. Washington:

Washington Up One:
Shots:  Washington 30, Boston 72
Goals:  Washington 1, Boston 7
Save %:  Holtby .903, Thomas .967

Score Tied:
Shots:  Washington 145, Boston 162
Goals:  Washington 11, Boston 7
Save %:  Holtby .957, Thomas .924

Boston Up One:
Shots:  Washington 32, Boston 11
Goals:  Washington 4, Boston 0
Save %:  Holtby 1.000, Thomas .875

There were major score effects during the series, as would be expected.  Including the brief period when Boston was down by 2, the trailing team outshot the team in the lead by the whopping margin of 107-41 and scored 12 goals in just 141.7 minutes of play for an amazing rate of 5.08 goals per 60 minutes.  The leading team managed just one goal (0.42 per 60), scoring on just 2.4% of their shots taken.

It is typical that the trailing team generates more shot attempts, but usually their percentages drop as they put more pucks on the net and take more risks, leaving themselves open to chances going back the other way.  For whatever reason both the Caps and Bruins were able to get away with almost everything in their own end when pushing for the tie.

The overall shot statistics flatter the Bruins a bit because they spent more time trailing.  Boston outshot Washington by 20% overall but by just 12% with the game tied.  It was still a very close series, and Washington was pushed over the top by an impressive effort from rookie netminder Braden Holtby.

The Chicago-Phoenix series was similarly close in terms of scores, but the underlying numbers suggest that balance of play wasn't nearly as tight.

Phoenix vs. Chicago:

Phoenix Up Two Goals or More:
Shots:  Phoenix 11, Chicago 11
Goals:  Phoenix 2, Chicago 1
Save %:  Smith .909, Crawford .818

Phoenix Up One:
Shots:  Phoenix 40, Chicago 76
Goals:  Phoenix 2, Chicago 5
Save %:  Smith .934, Crawford .950

Game Tied:
Shots:  Phoenix 73, Chicago 124
Goals:  Phoenix 9, Chicago 6
Save %:  Smith .952, Crawford .877

Chicago Up One:
Shots:  Phoenix 35, Chicago 30
Goals:  Phoenix 4, Chicago 0
Save %:  Smith 1.000, Crawford .886

In this series the Blackhawks outshot the Coyotes by 51% overall, and an impressive 70% with the game tied, yet somehow managed to get outscored 17-12 over the course of six games, as well 9-6 in tie-game situations.  The strong goaltending of Mike Smith compared to the inconsistent play of Corey Crawford was the decisive factor in the series.

Smith was particularly strong in game six, a game where everything was massively tilted in favour of Chicago except for the scoreboard.  I also found it interesting that Smith had the highest save percentage of any of the four goaltenders while his team held a one goal lead, which was perhaps unexpected given that the Blackhawks fought back three times to tie the game late in the third period.  Several posters in this HFBoards thread specifically downgrade Smith's first-round performance because of his supposed lack of clutch play in allowing late game-tying goals, but to me that's making the classic mistake of evaluating playoff performance:  Letting a few memorable events have too much influence while failing to properly appreciate the larger picture.

For the sake of comparison, Braden Holtby gave up a lead in five out of seven games, including twice in the third period, yet nobody would call him unclutch.  Allowing goals against in the final 10 seconds obviously has a huge negative impact on a team's win probability, but when 99% of the series is within one goal then every goal against has a major impact on the chance of victory.  Other than one third period in Chicago, pretty much every situation these four goalies have faced so far in the 2012 playoffs was a clutch situation.

Just as with Washington and Boston, the trailing team rode both a large outshooting advantage and insanely high percentages.  Overall, shots were 122-81 in favour of the team playing catch-up, with turned into a 10-4 advantage on the scoreboard.  That works out to a rate of 3.16 goals per minute for the trailing team, compared to just 1.26 for the team holding on to a lead.

In some respects it is amazing that Chicago even came as close to winning the series as they did, given that Phoenix's scoring rate per shot was over twice as high.  The repeated late-game comebacks to force OT kept them in it, but unfortunately the goaltending disparity was perhaps never more apparent than in extra time where Smith managed a .923 save percentage while Crawford put up a mere .813 and let in two very soft goals to help the Coyotes to the franchise's first second round appearance since 1987.

It would be interesting to see detailed scoring chance numbers or a breakdown of odd-man rush chances to see whether the leading teams were generating chances and just missing their shots, or whether their defensive focus meant they were not creating many dangerous opportunities to score.  In the absence of compelling evidence, however, I'd guess it was mainly a tremendous run of hot goaltending that kept the scores close (in both series combined, goalies on teams trailing by one stopped 97.3% of the shots against) and created 13 games of razor-thin margins in these two memorable series.

Sunday, April 15, 2012

Sitting on a Lead Isn't Working in 2012

Fifteen games in, the story of the 2012 playoffs so far has been third-period comebacks. Twelve out of 15 games have featured a one goal lead at some point in the third period, and in seven of those twelve games the trailing team fought back to tie. Five times the team that was trailing eventually ended up winning the game, four times in overtime and once in regulation (the Flyers' roller coaster 8-5 win over the Penguins on Friday night).

I would have guessed that the trailing teams were riding very high percentages to be able to put up those kind of results, but that's not actually the case. Both the leading and trailing teams so far have shot 8.0% in the third period with one team up a goal, although the leading teams' numbers are slightly inflated because of empty netters (the shooting percentage with a goalie in the net for teams up by one is 6.1%). The primary reason for all the comebacks is that the trailing teams have been absolutely dominant in terms of possession, outshooting the opposition 88-49. That is a rate of 39-22 per 60 minutes of play.

It is normal for teams to play to the score. According to Behind the Net's stats, the Nashville Predators were the only team in the league this season that did not have over 50% of the Fenwick events while trailing by a goal, and teams down by one had an outshooting advantage of 29.6 to 24.5 per 60 minutes. Those numbers include results from the whole game, and would likely show a greater split for third period results only (some of my past findings indicate that the shot rate skews even more in the third period alone).

Despite generating more shots, however, the trailing teams were actually outscored during the regular season (2.54 to 2.43 per 60 minutes), which indicates that playing to the score was the right move for teams holding a late lead. It probably should be noted though that in a regular season sample team strength might also be a factor, given that the better teams would be more likely to spend time in the lead than the league doormats, whereas the playoffs do not have the same broad range of team quality.

The regular season results give a trailing team shooting percentage of 8.2%, very close to the 2012 playoff numbers. During the regular season the numbers for the leading team went up to 10.4%, which indicates that the comeback teams in this year's playoffs have probably been a bit lucky or had their comebacks enabled by strong goaltending in the third period. That said, even if the leading teams' percentages rise as the playoffs go on, there will still be a lot of comebacks as long as the shot ratio remains in the vicinity of 2-to-1 in favour of the trailing teams.

Utilizing a collapsing defence to preserve a late lead is the best strategy in some cases, but some teams (Pittsburgh and Phoenix, perhaps?) are probably currently reviewing their game tape to determine whether their late-game play is doing more to help them than to hurt them. You can trade quantity for quality in terms of chances against, but if the quantity gets too high than some pucks are going to go in anyway and the strategy is no longer optimal. It will be interesting to see whether teams can improve their ability to hang on to late leads or whether the comebacks will continue in 2012.

Thursday, April 12, 2012

One of These Does Not Belong...

GoalieSv%MaxMinAvgPO Tms
M. Smith.930.974.851.926.936
J. Quick.929.963.881.927.930
J. Halak.926.963.856.931.937
P. Rinne.923.960.880.921.919
J. Howard.920.940.881.919.919
R. Luongo.919.949.869.920.930
A. Niemi.915.950.863.914.915
C. Crawford.903.931.867.901.896

Sv% is total save percentage, Max and Min are each goalie's best save percentage marks over seven consecutive games during the 2011-12 season, Avg is the goalie's average save percentage per 7 game stretch (naturally, this metric will track very closely with the overall save rate), and PO Tms is each goalie's combined save percentage against the other 7 Western Conference playoff teams.

The obvious takeaway is that there is some really good puckstoppers out West, with six teams possessing demonstrably above-average goaltending. That leaves just the San Jose Sharks with the very average Antti Niemi, and the Chicago Blackhawks, who look to be the one team in the Western Conference that is in a substantial amount of trouble in goal heading into the playoffs.

In a previous post, I pointed out that a typical Cup winning goaltender needs to put together a streak of approximately .930 over 600 shots. This season Crawford barely even managed to hit that during his best seven game stretch. His highest mark over 20 consecutive games was only .912. If the playoff version of Corey Crawford is the same one that showed up during the regular season, it is very unlikely that Chicago will get the percentages needed to overcome four straight difficult opponents and end up with a Stanley Cup. Chicago did manage to win the 2010 Cup despite Antti Niemi's mediocre .910 save percentage, but most observers would agree that version of the Hawks with multiple star players on ELCs was stacked compared to this year's roster.

That said, all hope is not lost for Blackhawks fans. Despite Crawford's mediocre play, Chicago still managed to go 13-10-3 against the other seven Western Conference playoff teams with him in net. That was still the second-worst record of any of the eight expected playoff starters (ahead of only Niemi), but it was not far behind most of the other teams as only Smith and Luongo managed to post a win percentage of .600 or better against that tough slate of opposition. Chicago has a very good team in front of Crawford, especially if captain Jonathan Toews is able to get back into the lineup and contribute at his usual level. In score-close Fenwick, one of the best measures of overall team strength, Chicago ranked 5th in the league.

The other thing to keep in mind is that Crawford acquitted himself quite well in the first round against Vancouver last year and had a much better overall season in 2010-11. Perhaps Crawford's true ability is closer to the .918 he managed in the 2010-11 regular season and playoffs combined than this year's .903, which would make him far more likely to be able to deliver Cup-calibre goaltending over the next two months.

For what it is worth (probably not much), Crawford finished the season strong with a .921 and an 8-2-1 record over the last two months, including six wins over playoff teams, although Chicago's offensive output of 32 goals in the 11 games and stingy shot prevention of 23.5 SA/60 obviously also played a major role in that recent success.

The Western Conference playoffs are as usual going to be a grind filled with tight games where hot goaltending can make a difference. The Blackhawks have a strong team that could be a contender, except for the question mark related to the fact that their goaltending this season has been well behind the rest of the teams in the mix out West. It seems safe to say that the pressure is on firmly on the shoulders of Corey Crawford because Chicago will likely need much better goaltending than they have been given so far in 2011-12 to be able to put together another Cup run.

Tuesday, April 10, 2012

Why Lundqvist Should Win the Vezina

Even Strength Save Percentage in 2011-12 by Division:

1. Northwest, .925
2. Pacific, .925
3. Central, .923
4. Northeast, .919
5. Southeast, .917
6. Atlantic, .916

Quick and Lundqvist ended up with almost identical situational save percentage stats (both .933 at even strength, with Quick just slightly ahead on the penalty kill .908 to .905). The Kings faced a higher percentage of shots against on the PK, which caused Lundqvist to slightly edge out Quick in terms of overall save percentage by the narrow margin of .001. The closeness of those results, combined with Quick's extra workload and the Kings' late-season playoff charge, has made Quick a recent trendy Vezina pick, an impressive comeback given that it looked like Lundqvist had the award sewn up by the All-Star break.

Assuming both goalies were competing in the same environment, it would indeed be very difficult to separate them by the numbers. However, if each goalie's numbers are adjusted relative to their individual conferences, then Lundqvist opens up a decisive edge over Quick:

Conference-adjusted situational save percentages:

Quick: .930 EV, .907 PK, .941 PP
Lundqvist: .936 EV, .906 PK, .974 PP

Multiplying those out by the league-wide average frequency of shots against in each situation, Lundqvist ends up with a conference and situationally adjusted save percentage of .932 compared to .927 for Quick.

Another option would be to adjust each goalie's numbers relative to their division, although in that case the much smaller samples means it would be important to remove each goalie's results from the overall numbers (i.e. the Pacific without Quick and the Atlantic minus Lundqvist). That calculation only increases the margin in favour of Lundqvist, given that his .933 looks much more impressive when stacked up against the combined .912 put up by the rest of the Atlantic division, with the other netminders in the Pacific still combining for an above-average .924 mark even without the contributions of that division's Vezina candidate. Using the divisional numbers and the same correction for shots against by situation, Lundqvist's adjusted number moves well ahead of Quick .935 to .927.

To me, anything close to a tie suggests Lundqvist should win because his elite track record means that it is much less likely that his terrific season was based on luck or other secondary factors. I would pick Lundqvist even assuming that both goalies faced identical shots against for this reason alone. Adjusting for the east/west disparity only makes the choice that much more obvious, in my opinion.

Relying on historical records to evaluate a single season of goaltending is somewhat unfair to the goalie who is four years younger, but it is simply the reality of dealing with uncertainty in goalie evaluation (and why I don't think single-season awards are all that significant). This was Lundqvist's third season in a row at .920 or better while Quick's previous career best was .918. Future years may well prove that Quick's true talent is in the mid- to upper-.920s, but as of right now that's probably not the smart way to bet.

Another relevant piece of statistical info is that Quick's numbers were much better at home (.936 at home compared to .922 on the road), whereas Lundqvist's numbers were higher away from home (.934) than at MSG (.926). That doesn't necessarily mean much, variance is naturally going to be higher over 900 shot samples than over full-season results, but since road numbers are counted by a variety of different scorers they are less likely to be subject to bias. It is also worth noting because both goalies have been pretty consistent on the road over the last three seasons, with Lundqvist maintaining a steady .011-.013 gap over Quick:

Quick: .915, .916, .922
Lundqvist: .926, .929, .934

This year Quick's home numbers shot up while Lundqvist's improved slightly. Again that could be reflective of improved play for both goalies, but it could also be partially related to shot counting or team factors. The other interesting thing to note is that this is the third straight year that Lundqvist's save numbers have been better on the road. MSG is known for poor stat recording in general and it is possible that his numbers are being at least partially suppressed at home, especially given that Lundqvist faced an average of 5.6 more shots against per 60 minutes on the road compared to at home in 2011-12, coming on the heels of a 6.0 difference in 2010-11.

On the other hand, Quick's shots against rates were 26.5 at home compared to 28.0 on the road in 2011-12. His shots against rate at home has actually increased in each of the last three seasons, at the same time as his road shots against rate has been continually decreasing. That's not the typical statistical profile of a goalie being disadvantaged by his home scorekeeper. Overall, the home/road numbers are just one more reason to be a bit more confident in the Swede than in the American.

Taking their histories into account along with the conference disparity, I think Henrik Lundqvist deserves to win his first best goalie award. It could be argued that the shot quality allowed by the Rangers was not typical of the rest of the Atlantic Division, or that goaltending in the Western Conference in general or the Pacific Division specifically was simply a whole lot better than it was out East, either of which would mean that the adjustments above are unfair to Quick. I would certainly listen to anybody willing to make those arguments, but right now I don't see enough supporting evidence on the table. Shot quality arguments are always particularly murky because of the lack of good data, and subjective comparisons are very difficult, particularly for two teams in opposing conferences.

As an aside, this season has made me wonder at times whether we can continue to rely on the general assumption that EV shot quality is relatively constant between teams. The two major pieces of evidence in that direction are probably St. Louis' 2011-12 goalie stats and the conference splits displayed above. In the aggregate I think 5 on 5 shot quality is still probably not all that important for most of the league, but if there are some significant effects on the margins that would be important to know for goalie evaluation.