No it has nothing to do with that. Its a different mindset because of the situation. If they mess up there is not much chance to come back from it. If you give up the tying/go-ahead run in any inning prior then the offense can still have at least a couple chances to come back. Its a different mentality that some pitchers can't handle. Overall the importance may be the same, but that doesn't mean the pressure isn't higher. I mean even as a fan you can feel the pressure of the situation in a close game in the 9th way more then the 6th, 7th, or 8th. When the Angels are in a close game, it isn't until that last inning when the pitcher goes out to close the game that I am on the edge of my seat, completely focused, not moving for fear I will jinx something. Imagine being the pitcher in that situation. Its just not the same as earlier innings regardless of whether or not it still means the same.