Arsenal boss Arsene Wenger admits he can't be sure who he will have available for tomorrow's noon showdown with Manchester United.

Theo Walcott and William Gallas are rated 50-50 for Arsenal's critical clash.

Walcott is struggling with a shoulder injury while Gallas is doubtful with a hamstring problem and a decision on both players will be made in the next 24 hours.

"We will not know about Walcott and Gallas before tomorrow afternoon. It is 50:50 for both," boss Arsene Wenger told Arsenal TV Online.

Mikael Silvestre broke his nose in Wednesday night's goalless Champions League draw with Fenerbahce and Wenger must decide whether to gamble on the 31-year-old defender against his former club.

"Mikael has a broken nose with an open wound on the side," said Wenger.

"Basically he should be capable of playing. But in the next 48 hours I will have to decide what we do.

"You cannot rule him out and I feel he can play. But I have to decide whether I go for the gamble or not."

Bacary Sagna remains a worry, but in a welcome piece of positive news in an otherwise gloomy medical bulletin Manuel Almunia has recovered from the sickness that forced him out against Fenerbahce.

"Almunia was back in training today so he will be available," said Wenger.

"As for Sagna, there was a gamble on him that I did not want to take last night.

"We could not take it today in training either. He still needed to be out of impact work.

"I think he should be OK for Saturday but there is still a slight concern."

Emmanuel Adebayor (ankle), Emmanuel Eboue (knee) and Robin van Persie (suspension) are definitely out of the clash with United.