The China comments were last year, and he then played almost every game after Arteta came in until the restart. I think that proves it's not a political issue, or a football issue.
The obvious answer is therefore his wages, and his refusal to agree to a wage cut. Since the 'leak' (surely from the club) that he was one of three players (the other two weren't announced) to refuse to agree to a wage cut, he hasn't played a minute. I assume that there must be some kind of game-bonus in his contract, so they're saving money by not playing him. I don't think it's the worst idea ever, given how much we're losing currently, and that he's been mostly ineffective for some time now. Though obviously it would have been easier if we could have agreed a loan or something in the summer.