I don't think it is surprising that Mauer was booed. I don't know if I'd call it outrage or frustration (and it sounds like he was frustrated himself). He has a line of .194/.380/.389/.769 with RISP in 2014. For his career, he has a line of .330/.452/.477/.929. So he has a pretty substantial drop-off this year. It isn't surprising that people would boo when he doesn't come through in the late innings with runners on base. And little posts like this one from Phil Mackey aren't going to quell the booing: Phil Mackey @PhilMackey 47m Per @Fangraphs, Mauer has been worth $500,000 so far this year. He was worth $26 million and $22m in 2013 and 2012. (D and position matter)