21 year old? needs to up his game. He's not a teenager anymore.
And before you start defending him.
Yes he is VERY good. Probably the best central midfielder u-23 but THAT IS NOT GOOD ENOUGH.
Remember that he is supposed to replace XAVI, the best midfielder the game has ever seen.
And he shouldn't. He's nothing like Xavi. He's a versatile midfielder. But he's an attacking midfielder first and foremost (which is what he was in his youth days), and then everything else. Busi, is in fact more Xavi than Thiago. But Busi is more needed at DM, meaning Pep (and L.Milla) is trying to make most of Thiago's versatility (and also because there isn't any other serious contender for the xavi role). And although he could go on to become a fine CM in time, his inherent talent will always remain underutilized such capacity.
Now the reason he put up an explosive show in pre-season is 1) He had the Euro-u21 momentum still with him 2) Pep gave him more freedom to express his talents, and greater license to attack. I really think 2011-12 should've been the Thiago year, where he makes a significant leap both in terms of development and importance to this team. But the pre-season form and momentum which we all hoped he would build on, was disturbed by the Cesc signing (won't go down well with Cesc admirers i know). Irv was the first one to point out, and its something i've deduced from how the events have unfolded, esp from the player's perspective. To fit in the Cesc factor, Thiago was forced to curb his natural attacking instincts, and embrace a deeper/defensive role for the team, and the other times too he remained conservative possibly from the fear of losing playin' time. And whilst his defensive side of the game and horizontal play improved, his offensive game suffered in the process, and has looked rusty in the final third. I wouldn't say Cesc signing was not useful, or wasn't needed. But his purchase has slowed down T's progress, who 'd otherwise be afforded a greater offensive platform to work his magic.
So whilst he has improved defensively, and worked on his discipline (he can still be a bit casual on the ball but its minimal), he's been disappointing going forward. Reason y it may look to a lot of them that he hasn't progressed since pre-season. Which in a way is true, because his natural game hasn't improved since pre-season, despite the positives .