We do at least have some decent players in reserve. Johan Djourou's performances while filling in early in the season (when Gallas was covering at left back) probably deserve a recall, but Phillipe_Senderos is back from injury now so is expected to start alongside Kolo Toure.

When explaining Freddie Ljungberg's absence for the Newcastle game on Saturday, Arsene Wenger said that he expected him to be ready to play tonight. He's very short of match fitness now, not having played for 5 weeks, so will probably be on the bench to give us something different.

Gilberto was expected back from his family problems in Brazil, but Wenger was planning on leaving the decision till late, to see what kind of state he's in.

Robin van Persie's foot injury, sustained just before half time on Saturday, is not as bad as first feared. But there's still a good chance he'll miss this game. And Tomas Rosicky has returned to training following his hamstring problem, but is short of fitness for tonight (Wenger says he should be ok for Bolton on Saturday).

Abou Diaby and Lauren are both expected to be out for the rest of the calendar year.

So... options may be limited tonight. The defence picks itself with Lehmann, Eboue, Toure, Senderos (or Djourou) and Clichy. If Wenger wants to play 4-4-2 then Henry can play with Adebayor, but it's not clear that this would work in a 4-5-1 where he prefers van Persie's flexibility as a wing man. Maybe Baptista would start again as an attacking option from midfield, but he didn't have a great warm-up for it on Saturday when he looked somewhat unsure of his role.

Mind you, if Gilberto, Ljungberg, and van Persie are all out along with Rosicky, the midfield choices will be limited anyway. Cesc and Hleb are the only definite starters, though Flamini can fill in for Gilberto. If none of those other options are available, one possibility is to use Justin Hoyte as a full back, pushing either Eboue or Clichy forward to give us width in midfield.

Hamburg have lost all 4 games and don't even have the possibility of a UEFA Cup place for finishing 3rd. That's how even this group has become between the other 3 teams (see table).

Of course, the pressure is off of Hamburg and this could work in our favour or against us. We have to trust that having the pressure on us is what will make the most difference, and in a good way. Hamburg have some dangerous players, especially Dutchman Rafael van der Vaart who scored Holland's equaliser against England last week. But they'll miss the likes of Vincent Kompany (achilles), Nigel De Jong (cartilage), and Juan Pablo Sorin (thigh). Former Arsenal youngster Guy Demel also missed the game through injury.

The group situation will be much clearer after tonight. As things stand, we're level on points with Porto (and we've beaten them once already), but we're a point behind CSKA (and we've lost the head-to-head matches).

So... if we get as many points as Porto tonight, we'll still be level with them, and will only need a draw in the last match at their place.
That's the simple version, there are complications depending on CSKA's results but they're simplified if one assumes that they're not going to lose their last game, at Hamburg. If we and Porto both win tonight and draw the last game, all 3 teams could finish on 11 points - but that's good for us on the goal difference side of things since Porto's 7 goals against Hamburg wouldn't count, and we would be bound to go through. Another complication arises if we win and Porto lose tonight, but again it's a good one in that we could afford a one-goal loss in Porto but still go through on the head-to-head.

On the other hand, if Porto do better than us tonight, against CSKA in Moscow, we'll go into that last game needing a win (any win).

So, our result vs Porto in the final game is more important than our result vs Hamburg. Winning vs Porto will always see us through, while losing vs Porto will see us out in all but one scenario, and a 2-0 defeat (or a worse than 2-goal defeat) in that final game will see us go out even then. Moscow beating Porto would mean we don't need such a good result vs Porto, but would mean Porto would need the result too in the final game, and would make it unlikely for us to finish first in the group. Finishing first in the group is however the least of our worries right now.

(Thanks to Ben Fairweather for his help with this)