Sky Sports is saying Arshavin out for three weeks. Cesc fears his season is over and Gallas will likely be out for the same time he was already, or longer, since it's a recurrence of the same injury. So, maybe 6+ weeks? That's the rest of the season as well. (Unless they make the Champions League Final maybe lol).
Would Wenger even think about starting Sol Campbell at the Nou Camp? Is Silvestre injured? He might just play Song there again, but that makes their midfield so much weaker..
This is where Arsenal's title challenge stumbles I think, they'll slip away in the next few games and it'll be a two-horse race.
However, despite those absentees, I can't count Arsenal out just yet. Barcelona will be missing Puyol and Pique, so if Arsenal ever had a chance to get at Barca, it'll be in the return leg. There's still a chance that Abidal and Iniesta won't make it, I hear, so they could be just as big a problem for Barca and Arsenal's injuries are to themselves.
Obviously, Barca are still strong favourites as Arsenal have to win (or draw 2-2 for ET, 3-3 to go through etc). But we'll see. If it's anything like the first leg though, Barca probably won't throw away so many chances again.