A couple of things to keep in mind.
The league as a whole "hits" better w/RISP. Sacrifice flies don't hurt a player's batting average (or OBP/SLG), a typical flyball with the bases empty that would drop a hitter's average no longer does if a player happens to be on 3rd at the time and scores.
Another, intentional walks almost always occur with someone already in scoring position. In Mauer's case, every IBB in his career has come w/RISP, this inflates the w/RISP OBP relative to his overall line. So he didn't really "hit" better in those situations.
The IBB would affect his OBP but not his slg% and BA...that's all based on actual at bats. Not only that, but to say they don't matter would be to assume he would have gotten an out in every instance when he was IBB....which would be a strange assumption based on the results he has when he isn't IBB.
'a typical flyball with the bases empty that would drop a hitter's average no longer does if a player happens to be on 3rd at the time and scores.'
Doesn't affect his BA/OBP/SLG% RISP numbers though...and there's an assumption there that if the guy had been on 2nd instead of 3rd, he wouldn't have gotten a hit instead of sacrificing himself.
BTW, all these scenarios, apply to everyone...
Edited by ThePuck, 12 February 2013 - 12:46 PM.