Ever notice that clutch players are already really good?
Seriously, every single person advanced in this thread as being "clutch" are already among the best athletes today. David Ortiz is one of the most feared hitters in baseball, whether it's the first or ninth inning. Derek Jeter is going to be a first ballot Hall of Famer. Joe Montana was one of the greatest QBs of all time. The list goes on and on. You never hear about some fragile and weak RB suddenly becoming an explosive and feared runner in close and late games. You never hear about scrappy defensive shortstops who hit .220 on the season having a long and established career average of .400 with RISP.
Everyone who plays professional sports today are already among the top athletes in the world for the very fact that they made it far enough to play professionally. That tends to weed out a ton of the headcases who collapse under pressure. Guys like that don't tend to last in sports; they instead drop out of it before even sniffing the pros.
I think people view clutch in a way that's erroneous in four ways.
1) It is wrong to think that clutch players are people who are able to go above and beyond their performance potential. While athletes are pretty much at the top of the food chain when it comes to speed, strength, and so on, even they have their limits. If these people actually existed, you would see judy hitting shortstops hitting game-winning home runs on a regular basis. Rather, we have to remember that these guys are already talented.
However, there is something that does not go against this line of thinking that I am willing to believe in. While someone might not be able to go above and beyond their performance boundaries, they are able to maintain those levels or even drop well below those levels. If you made Mariano Rivera a 7th/8th inning setup man, he still would be one of the best relief pitchers in baseball. He is able to carry his talent and performance into pressure situations into the ninth inning. Adam Vinatieri has a 82.5% success rate as a kicker; he is able to bring that success into close and late situations.
On another level, some players will delve below their performance levels in pressure situations. Who these players are is up for debate (more on this in a second), but I think we can all agree that this is true for certain people.
2) Fans and observers are strangely finicky. We have selective memories. The media is happy to play on these notions, as people will happily gobble them up. We remember David Ortiz hitting big game-winning home runs. We remember Jeter legging out an infield hit to start a big comeback rally. We remember Adam Vinatieri hitting Super Bowl-winning field goals.
However, people tend not to remember the failures of certain people. If David Ortiz strikes out with two men on base in the bottom of the ninth inning during a game, people will forget about it the next day. The same goes for when Jeter strikes out in a similar situation. Nobody remembers Joe Montana's interceptions in close and late games.
Conversely, people will be all over certain players in similar situations. If A-Rod struck out in that situation, he'd be crucified the next day in the NY Post, with Mike Celzic spewing out approximately twenty articles a day talking about how un-clutch A-Rod is. Prior to his winning the Super Bowl, Peyton Manning throwing an interception in the 4th quarter of a close game would see him strung up by the various talking heads.
However, on a similar and really weird note (because of reputation or whatever, I do not know), we treat them differently when they succeed in these situations. If the Yankees are down 5-1 and A-Rod hits a two run double which helps lead the Yankees to a 6-5 comeback, it'll go unnoticed. When Peyton Manning would lead the charge on any game when the Colts rallied back after being down, nobody would bat an eye. People either ignore these facts or they write them off as mere flukes.
In this case, clutch is all about perception.
3) The biggest problem with clutch moments is that we only have small (albeit memorable) sample sizes to go by. There is a lot of difficulty in attempting to quantify clutch simply because these instances are few and far between. Maybe 8-10 games for an NFL player or 30-50 ABs might seem like a lot, these really are inadequate numbers to create an accurate model to put a label on "clutch" which is more than just an arbitrary designation placed on a player. Perhaps it seems like a guy always gets big hits when they are needed. The problem lies in the word "seems". We could be making a completely unfounded judgment on a player based on our own memories and perceptions, which are subject to all sorts of flaws.
We have no set definition for what is clutch or who is clutch. There are no bright lines marking off the boundaries between those who are and those who are not. Is a guy clutch because he gets big hits when it matters? Is he clutch because he always gets hits when his team has runners in scoring position? Is he clutch because he somehow always manages to make a three point shot within the waning moments of a game?
All of the statistical evidence that has been compiled so far is inconsistent at best. I will happily grant that it's stupid to assume something does not exist because we lack hard statistical evidence for or against its existence, but I will equally grant that it is stupid to say something exists despite the fact that we have no statistical evidence to back up that assertion. If you want to prove something actually exists, you need more than opinions.
4) I think this point is the most overlooked point when it comes to the assertions of being clutch. Sports are about much, much more than just single teams and individuals. I think that people focus way too much on a single person in certain situations in this debate, to their detriment.
Sports involve teammates and the other teams! Context is absolutely critical to making these assertions. Maybe Derek Jeter got a game-winning single in a given game, but the guy he got it off of was a pitcher with a 7.23 ERA and the first baseman was sorely out of position to field the ball cleanly. Maybe Tom Brady led the Patriots to a big comeback victory on the road, but it was against the Texans and their anemic defense. Adam Vinatieri could have nailed a game-winning field goal, but the rest of the Colts could have stunk up the joint for most of the game and nearly blew the game on their own. A-Rod may have struck out in the bottom of the ninth of a 4-3 game with two runners on base, but he drove in two of those runs with a double much earlier in the game. Michael Jordan might have hit the game-winning shot, but his coach drew up the perfect play which the rest of the team executed flawlessly.
You absolutely, positively cannot look at these players in a bubble. A guy might get the "clutch" label for hitting five game-winning HRs in a season, but he only did so when he faced terrible pitchers. A guy like Peyton Manning might get a bunch of the blame for his team's playoff woes, but lost amidst the criticism was the fact that his running game was ineffective at best, the defense played piss-poor, and the coaching staff refused to adjust throughout the course of the game.
If you want my honest opinion, I think clutch exists at some level, but I also think people overrate it to an insane degree. I'm happy to admit luck exists, too. The two are not mutually exclusive.