He was boo'ed the other day mostly out of frustration that our team gave up 3 goals in 15 minutes, despite none of them being his fault really. He was singled out specifically because he has shown very little hustle this season, he'll often get beat on the dribble or forget to cover his mark and instead of rushing back to help make a play he'll just stand there and watch the other team score. It was the same thing with Henry at the beginning of the season, he was boo'ed not because of the quality of his play, but because he spent more time walking around than hustling. Unfortunately while Henry took the fan criticism and used it as motivation, Rafa got frustrated and lashed out at his teammates. I feel like part of the incident might have to do with him not being comfortable with English, though.
Its also worth pointing out that the last 4 times NY has kept a clean sheet Rafa was not in the lineup. Expectations are also very high for him because he literally makes 4.6 million dollars a year while most of his teammates make between 75-250k. Last week his salary was 1 million dollars more than the entire other team. For that kind of investment, I think the fans are fair in expecting some hustle...
He's apparently not getting along with the coach either, so I wouldn't be surprised if he moves again over the winter/summer.