Arsenal will go into it with Cesc Fabregas as a big doubt.
He didn't appear in training because at the moment he is not fit to play. We will give ourselves 24 hours more and we will assess the situation tomorrow. But today he would not be available. Sometimes you do not want to take a gamble in training because 24 hours more can help. You don't want him to get another kick so it was better that he didn't train. I would say it is 60 against, 40 for him playing.
Barcelona will be missing Andres Iniesta, so instead of playing the 4-2-4ish formation that they had been playing recently, they will play in a more traditional 4-3-3, with Xavi, Sergio Busquets and Yaya Toure, the last 2 as holding midfielders, with Toure a little higher advanced than Busquets. Up front it will be two of Ibrahimovic, Henry or Pedro with Messi on the right. If Pedro comes in for Ibrahimovic, Henry will play as a false nine, as he has in their 4-2-4ish formation.
For Arsenal, Andrey Arshavin and Samir Nasri should start after training. William Gallas could start as well, and if he can, he should. If Fabregas does not play, I think Samir Nasri will come in for Fabregas in the midfield, and Tomas Rosicky will play on the right wing. Alex Song will be restored to his midfield position, and hopefully Abou Diaby will be fit enough to start in the midfield as well. Nicklas Bendtner will start up front.
Both sides obviously play the same style of football, so it may come down to the managers out witting one another. One thing that Arsene Wenger could do is play Andrey Arshavin on the right flank and play either Samir Nasri or Tomas Rosicky on the left flank. They both have more defensive awareness than Arshavin, and with Messi on that side, tracking back will be important.
Arsenal (4-2-1-3); Almunia; Sagna, Gallas, Vermaelen, Clichy; Song, Diaby; Nasri; Arshavin, Bendtner, Rosicky
Barcelona (4-3-3): Valdes; Dani Alves; Puyol, Pique, Maxwell; Xavi, Yaya Toure, Busquets; Henry, Ibrahimovic, Messi