Once upon a time, there was a goalie in the Quebec Major Junior Hockey League who was a highly-touted prospect. He played 35 games as a 16 year old and then attracted a lot of attention with a great year as a 17 year old. He was named the best defensive player in the Q and his team won two playoff rounds before losing in the semifinals. At the end of the season, the goalie's name was the first one called out in the NHL entry draft. Everything looked very promising indeed.
Then this is what happened to him in big games (playoffs and international hockey) over the next 5 seasons:
18 years old: 0-4, 4.47, .904 in a first round loss, plays fairly well at the world juniors but loses in the gold medal game
19 years old: 1-3, 3.31, .886 in a first round loss to a #7 seeded team, let in 6 goals on 30 shots in brief taste of AHL playoffs, scores the game winning goal on himself while stopping 24 of 28 shots in a loss in the gold medal final at the world juniors
20 years old: 0-2, 4.37, .843 in the AHL playoffs, loses starting job to Andy Chiodo
21 years old: 2-3, 3.47, .883 in the AHL playoffs, loses starting job to Dany Sabourin
22 years old: 1-4, 3.76, .880 in first taste of NHL playoff action
That's nothing short of awful, right there. Surely this guy would never be able to accomplish anything in big games, right? Let's continue:
23 years old: .933 save percentage as his team goes to the Stanley Cup Final
24 years old: Stanley Cup champion
I'm sure you have already recognized the goalie as Marc-Andre Fleury. I don't know of any other elite goalie prospect with a worse pre-NHL playoff career than Fleury. People often like to criticize goalies by saying that they have "never won anything"; Fleury not only didn't win anything, but he pretty much actively helped lose everything that he was involved in. Yet today he is considered by many to be one of the game's best pressure performers. I can recall in particular a few exceedingly dumb columns written by sportswriters arguing that Fleury's amazing clutch abilities should have made him the starter for Team Canada over Roberto Luongo in the medal round after the U.S.A. loss, even though their arguments boiled down to little more than "1 Cup > 0 Cups".
If one was to argue that Marc-Andre Fleury is clutch, then it would seem to be difficult to also claim that past clutch performance is a great predictor of future results. This is a sample of one, I recognize that, but the extreme nature of the results at both ends would still be pretty unlikely if goalies are truly consistent in pressure situations. The only way around this would seem to be to claim that everything that takes place before the NHL doesn't count at all, or to claim that something changed with Fleury as he got older, he "learned how to win" or something like that. The natural follow-up question to that would be that if Fleury was able to so easily escape his past failures, what's to stop any other goalie from deciding to do the same? Again, that would not reflect particularly well on the value of using past playoff successes to predict future ones.
No doubt some clever sportswriter could craft some eloquent narrative about how Fleury learned to "play within himself" and realized that "he didn't have to make all the saves, just the important saves", or possibly that he was "mentored by a veteran backup/goalie coach/teammate who taught him the mindset of a champion." I think he just had Crosby and Malkin on his team. We'll see if the Pens can make a third straight run to the Finals, the door appears to be wide open for them and so far they are 5-2 despite Fleury's .889. No doubt that would lead to a lot more veneration of this "modern-day Grant Fuhr".