I just don't get how you can't see how most importantly his lack of a defined role on the team hurts his performances. He came at a time were it was near impossible to bench Xavi, Iniesta or Messi, all three players who operate in the same space he does. So with players doing the same thing he did at Arsenal and what he was expecting to do here, can you not see how it would be extremely challenging to have a role and identity that is your own when you have those players constantly playing over you and a lack of continuity in a position so you can develop a role, an identity?
You can make the same argument with Messi, he was terrible anytime we played him on the RW and when he's back in the center against Bilbao, his performance was overall better. Its the same thing with Cesc, Macherano, Iniesta on the LW, Neymar on the RW. When you continually play players out of the positions that suit their strengths, their performance suffers.
For those saying his style doesn't suit Barca, I simply don't understand how you can make that assertion. He was clearly the best midfielder in the Premier League when he left and there were times when he drug Arsenal on his back to victory. Remember his game against Milan in 2007? He's too slow? There was a noticeable difference with the pace we played with in the first half and the second half of the season and a lot of it has to do with Xavi. He slows down moves and keeps our game flat and predictable much more than Cesc does.
He can't play in tight spaces? Its because he is usually playing as a CF with 4 players to beat. When he has space to move the ball out from deep and see the entire field, he can excel.
Despite his difficulties here, I think this season in particular he has improved. His indifferent form recently has a lot more to do with tactics and Xavi then him failing to fit in to the team. How you can say a player who grew up playing in Barca doesn't suit Barca is beyond me. Its not like we talking about a Mikel Arteta or someone who just clearly isn't world class. The fact that he produces his best spells in the beginning of the season when he is playing as a CM his evidence that not only does he belong here but he can excel if we give him a chance.