David Ortiz comes through with a timely grand slam tying the Red Sox / Tigers game in the 8th inning of Game 2 of the 2013 ALCS and the debate over the existence of "clutch" re-emerges.
A "clutch" player has been defined as someone who performs better in high pressure situations when the outcome of the game hangs in the balance. If that's the argument, one must show that in high pressure situations a player's statistics are demonstrably better than in normal situations. Proponents of clutch have failed according to Nate Silver as he notes the numbers don't hold up. It is therefore impossible to label Ortiz, or anyone for that matter, "clutch". At least by that definition.
I think most people agree the default outcome of a player in a high pressure situation is failure. We label those who fail consistently as "chokers". Therefore, in my opinion, if a player can consistently maintain their production despite the increased pressure then they should be called clutch. Under that definition Ortiz is a clutch hitter.
* Interesting side thought: If Saltalamacchia doesn't drive in the winning run and the Sox end up losing that game, do we even have this conversation?