Yap, there is a clutch rating. But I do not know how it does affect the gameplay. I know that there are clutch moments in the game engine as well (the video animation changes for them) but I only saw ONE clutch moment occur since playing MLB 2k12 where Matt Holliday hit a two-run HR to turn the game from a 3-4 deficit in the 9th into a 5-4 lead winning the game. I had more situations where I or the AI was able to turn the things over at the end of the game but those situations were not clarified as a "clutch moment".
As far as I can say I know some situations where the commentators talked about "clutch players" and refering "clutch" to hitting with RISP.
To me these are two different things:
1) clutch in the sense of crunch time (only at the end of games)
2) clutch in the sense of hitting with RISP (over the complete course of the game)
Both does not necessarily have something to do with each other (although it can of course).
When you look into the game the most players have really low clutch ratings (nearly no one is rated below 35, but most of the players have a clutch rating between 35-50) while high clutch ratings are really the exception (don't know anyone with a clutch rating above 85, Pujols has 84).
Also players like Tim Lincecum or Ryan Braun have a 35 clutch rating by default, I do not know what the coders or the rating guys have thought when they did this, since Lincecum isn't the only elite player with so damn low clutch rating.
So I do not really know if this clutch rating has anything to do with the comeback engine. If I knew how to edit the scripts to turn down this engine in 2k's games I would really try to do it, but I don't.

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