on the part of the OOTP player. When some 9th batter with a .220 average and ratings like a little leaguer comes up in a key situation, you are thinking "hey, we're going to get out of this". When that guy drills a triple, you are thinking "man, that was a clutch hit". If he comes up at the start of an inning, you think "hey, should be an easy out", and he singles or draws a walk to start a rally that wins the game, same deal.
In other words I agree with the spreadsheeter view so well-expressed here, especially as applied to OOTP. Derek Jeter is a clutch hitter who just happens to hit .300. But I also remember one of my favorite players was Mike Gallego, who didn't ever seem to hit over .250 but seemed to get a hit at just the right time.