The French international took part in training today, but was not involved in any ’contact’ work with other players and still faces a crucial make-or-break session tomorrow.

But given that he was initially only rated as having a 20 per cent chance of playing, his current odds are therefore a considerable improvement.

Wenger revealed: “Vieira is 50-50 today. He took part in training this morning, when we protected his ankle a bit, but he’s better than expected.

“At the moment, it is looking good. If he doesn’t have a bad reaction to today’s training, he will go a step further tomorrow and then I will make a decision on Sunday.

“They first told me it was a three-week job, so I thought it was nearly impossible for him to play on Sunday.

“But to have him in the side for a big game, you know he has the experience and he’s seen it all.

“He has the impressive physical presence that you want as you know the commitment will be top-level. He can be technically good and physically strong.”

If Vieira joins Gilberto Silva on the absentee list, teenager Cesc Fabregas may have to play his third game in eight days, although 20-year-old Mathieu Flamini or Robert Pires are other options.

Edu, Thierry Henry and Pires should at least recover from the knocks sustained during the midweek Champions League tie away to Panathinaikos.

Dennis Bergkamp should come back into the side after missing that trip due to his fear of flying, but Gael Clichy (ankle) is still out and reserve keeper Manuel Almunia (shin) is doubtful.

Arsenal (provisional squad): Lehmann, Almunia, Taylor, Lauren, Hoyte, Cole, Campbell, Toure, Cygan, Senderos, Vieira, Fabregas, Edu, Flamini, Ljungberg, Pires, Pennant, van Persie, Henry, Bergkamp, Reyes.