Some good news, some bad.
Fabregas will, it seems, lead the side out. Arsenal fans will dread a further injury to the captain as much as they dread an avalanch of goals. You just hope that he has not been rushed back, that this is not an act of desperation, because the season might not end with defeat tonight, but if Cesc Fabregas is ruled out for another few weeks, it will be as good as over.
Surely more desperate still is the surprise inclusion of Van Persie in the squad. Very strange to see the Dutchman back in contention ahead of schedule, rather than the opposite. He probably won't start, but if he does, it would not constitute a great vote of confidence for Bendtner and Chamakh.
Still, at least this latest injury news has provided for a bit more cautious optimism. Then again, with Arsenal holding a slender lead, discipline is going to be key, and from that viewpoint the absence of Alex Song may be more significant than the presence of Fabregas and Van Persie. Song remains the only player who can patrol the area in front Arsenal's defence with true competence. Wilshere and Fabregas never lack for workrate but their instincts are more attacking.
The contenders to step in, it seems, are Diaby and Denilson. Both endured something of a failed audition on Saturday against Sunderland. Diaby is like a lot of Arsenal's midfielders, in that he is too forward-thinking to be an obvious midfield anchor. He does have size on his side, but does not really enjoy the physical element of the game, probably because he has been injured so many times. He also lacks Song's ability to keep the play ticking over with simple passing. Too often, Diaby overcomplicates with too many touches and a general air of nonchalance that Barcelona's hectic pressing could well expose.
Denilson is the more conservative of the two, but lacks Diaby's imposing stature. He often looks lightweight in the Premiership, but that may not be such an issue against a team that threatens more with finesse than power. He has provoked the fans' ire many times both this season and last, and even felt the sting from his own captain after some inept play against Leeds. For a nominally defensive midfield player, he does have an unfortunate tendency to conjure goal-costing errors, and like Diaby, can project the impression that he is not really that bothered. This is not a game of beach soccer in Rio, it's a Champions League knock out game, so you'd hope that he is in a focussed mood if selected.
Given the choice, I would give Denilson the nod. Diaby does, despite his irritating style, have a certain X factor and can be difficult for the opposition to deal with. But in the absence of Song, Arsenal need someone reliable and disciplined. And Denilson is... well, he's more reliable and disciplined than Diaby. He has been tasked before with protecting the back four and his style, in comparison to the improvisational Diaby, is more suitable to a fluid passing game. Arsenal will need to hold on to the ball for a minute or two at some point.
Even if Denilson can rediscover some of his best form, Song's injury remains a massive blow. He was absent at the Nou Camp last season aswell, and that night, Diaby and Denilson failed to stem the constant tide towards the Arsenal goal, as Messi plundered a four goal haul. The Argentine will look to drop off into the very area that Song usually inhabits, and Xavi and Iniesta will relish the possibility of extra space there too. In the last few seasons, it has sometimes seemed that Arsenal only have a midfield in the attacking sense, and that the back four enjoys little to no protection when the opposition breaks. But Jack Wilshere's industry and maturity has contributed to an increased solidity in this campaign, and it's a pity that the first-choice trio has been broken up at such a vital time.
Arsenal lack a really tenacious ball winner at the best of times; without Song, I can't see them holding Barcelona. And as stated before, Walcott's injury is hugely unfortunate too, because his pace would have had you believing Arsenal could score one or two. Without that threat in behind, I'm not so sure.
All that you can ask is that Arsenal give it a good go and attack with pace where possible, without doing it in a naive way. It's a balancing act they pulled off pretty well at the Emirates, and it's worth remembering that the brilliant breakaway winner happened with Walcott off the pitch. Nasri might look to be a bit more direct than he's been in recent games, while Arshavin does make plenty of runs behind defences, as we saw at the weekend. If Fabregas can find the space and time to thread some passes through, Arsenal should make chances- especially with Barcelona's patched up defence minus Puyol and Pique. With Barca's wealth of talent, it depends more on what happens at the other end. With a great slice of luck, it could be a great night for Arsenal, but whatever happens, it should be a memorable game.