Part of the problem is the simple lack of opportunities: Cesc's minutes typically come at the expense of Iniesta or Xavi, which is to say, Barça is usually worse with him on the field than it would be with an alternative. Inevitably, this means more cameos and fewer chances. That problem is solved today, and hopefully he can take advantage.
But another problem is that Fábregas just doesn't seem to be perfectly in-synch with a lot of his teammates. Iniesta and Xavi have been hurt enough to give him consistent playing time in the middle of the field (at least periodically), but even then he's never been brilliant. (I suspect he would look better without Messi on the field, a theory that will be put to the test today; however, if there's any truth to it, Fábregas's future at Barça is pretty much hopeless, so let's just put that aside for now.) There was an interview a few weeks ago in which he explained the lukewarm reviews to as follow:
When Guardiola retired, Xavi had a tough time. No one understood his game well and he was criticized. Now he's one of the best players in Barça history. People take a while to get accustomed. With Iniesta something similar happened.On the one hand, the call to not overreact (which was emphasized throughout the conversation) makes complete sense, but the idea that the problem isn't his game but the fans' perceptions is jarring. Perhaps that's just a rationalization that's easier on the stomach than the alternative: "I'm good, but compared to the group here, I guess I'm not quite that good." Maybe it was just an empty thought that filled the space in the interview. But it's an odd explanation, nonetheless. He's essentially saying, "I'm different, I'm English (in style though not nationality), settle down, you'll get used to it." But he's the one searching for a place on the one of the best teams ever, a team with a very distinct approach to the game. It's a philosophy he should know well, given his upbringing, and he's been there for more than a year now. If it's a matter of styles clashing, Fábregas is the one who needs to give ground, not the fans. If a resolution is only a matter of patience, fans shouldn't have to wait a year and a half.