Mathieu Flamini will miss Arsenal's Barclays Premier League clash with Manchester United on Sunday because of an ankle problem.
Flamini sustained the injury during Tuesday's heartbreaking Champions League quarter-final defeat by Liverpool and is expected to be sidelined for three weeks.
Brazil international Gilberto, who replaced Flamini in the 43rd minute at Anfield, will also deputise for the trip to Old Trafford.
"I believe Mathieu will be out for three weeks," Arsenal boss Arsene Wenger told Arsenal TV Online today.
"It's a big blow but Gilberto has a lot of quality and experience and he will come in. Gilberto can help the team recover and focus."
Dutch striker Robin van Persie is available to start against the Premiership leaders but defender Bacary Sagna is missing with an ankle problem.
Losing Flamini is a major setback for Arsenal who must topple United if they are to have any hope of escaping a third successive season without silverware.
Sir Alex Ferguson's side are six points ahead with five games remaining but can not afford to slip up at Old Trafford with Chelsea in hot pursuit.
Another defeat would conclude a depressing week for the Gunners whose Champions League aspirations were dealt a mortal blow by Liverpool.
Wenger's claims that Arsenal can still win the title have been universally dismissed but Gilberto is adamant his side have not given up hope.
"It's a big game. Maybe things can happen - you never know," he said.
"The important thing for us is to try to forget what happened against Liverpool.
"We still have a chance to win the title but it's important that we win all five remaining games. If we do that, why not?"
The only comfort Gilberto can take from the defeat at Anfield is the invaluable lesson it will have taught his young team-mates.
"Sometimes you learn more in defeats and nights like Tuesday than when you win," he said.
"But of course no one at this club enjoys it when we lose or miss the opportunity to play in a Champions League semi-final. We will all learn from this result."
Jens Lehmann's remote hopes of figuring during the run-in now look dead and buried after the German goalkeeper attacked Wenger for keeping him on the bench against Liverpool.
Lehmann, 38, rejected a January move to Borussia Dortmund in a bid to reclaim his place from Manuel Almunia but the Spaniard remains first-choice stopper.
"I stayed here to win the Champions League and I saw good chances to play, but I have not had these (chances) and that makes me very angry," he told Germany's Kicker magazine.
"To be sitting on the bench behind somebody who only started to play when he was 30 is not funny. I am very angry.
"If the coach had spoken to me before the start of the season then I would have been able to decide if I wanted to sit on the bench.
"He has a different opinion and I don't really believe he can be happy with it."
