Battle of California links to ESPN's expert predictions for this upcoming season, and points out that the Dallas Stars were picked by 5 out of 6 writers to win their division, and 2 of them predict them to win the Cup. The Philadelphia Flyers were picked by two writers to win their division, and one of them to win the Eastern Conference.
What do those two teams have in common? They were playoff overachievers, rising from the #5 seed in their conference to make it to the Conference Finals. "It's amazing how much public perception can change with a little playoff success," wrote jamestobrien at BoC, and he is certainly right.
But is there any justification for those picks? Does a Cinderella playoff run mean great things the next season? I decided to look at the issue in more detail, and the answer is, in nearly every case: No, it does not.
In the last 20 years, 23 teams have reached the Conference Finals despite finishing out of the top 4 in their Conference in points. Those 23 teams averaged 87 points in the year they made their playoff run. The next year, the average points for the same teams was just 81.
Twelve of them (over half) did not even qualify for the playoffs the next season. Nine of them had major declines the next season (drops of 10+ points) while only three of them improved by at least 10 points. The teams that improved were Anaheim in 2005-06 (who traded for Chris Pronger and won the 2007 Cup), Boston in 1991-92 (just had an off-year sandwiched between 100 point seasons), and Chicago in 1988-89 (which was the only instance of a team coming together during a playoff run and significantly improving the next year without major additions).
Of the teams that did manage to make the playoffs again, most of them went out in the first round. Only 4 of the teams returned to the Conference Finals the next year ('07 Ducks, '98 Sabres, '91 Oilers, '89 Hawks), only 2 of those teams made it to the Finals (Ducks and Sabres), and only the '07 Ducks won the Stanley Cup.
Unless they added an elite player or had a Hall of Famer in goal, every single lower seed that overachieved in the playoffs did not make it as far the next time around. Most of them didn't even make it back to the playoffs in the first place, and nearly all of those who did qualify simply failed to duplicate the postseason magic.
If we look closer at both Philadelphia and Dallas, I think they are likely to continue the same trend. The Flyers were outshot 2604-2359 last season. They held their heads above water because of a 10.4% shooting percentage, and a .915 save percentage from their goalies. They have some young talent on the team so they could have some internal improvement, but I highly doubt they match either their shooting percentage or save percentage next season, which will result in a decline in the standings.
The Stars had a +37 goal differential, which was the third-best mark in the entire NHL after Detroit and Montreal, which indicates they weren't an ordinary #5 seed. However, Dallas led the NHL in shooting percentage (10.8%), which is why they outscored their opponents despite barely outshooting them (2187-2128) and only getting league-average goaltending (.908). Even with some regression to the mean in terms of scoring the Stars should be competitive in a tough division, but I don't think they will repeat either their 2008 goal differential or 2008 playoff success.