LONDON -- Laurent Koscielny could be sidelined for weeks with a "serious" Achilles problem, Arsene Wenger has warned, potentially dealing Arsenal a massive blow entering the final months of the season.

Koscielny had to come off at half-time of Arsenal's 2-2 draw with Manchester City on Sunday after the recurrence of an Achilles injury that has kept him sidelined several times in the past. Wenger said the France centre-back still needs to undergo a scan, but that he could face a lengthy layoff.

"It is certainly serious," Wenger said Tuesday at his news conference ahead of Wednesday's Premier League game against West Ham.

"If he's ruptured a few fibres of his tendon, it could be a few weeks. If it's just an inflammation, he could maybe be available for selection next week against Crystal Palace. I think he has a scan today and we'll know much more tomorrow."

Goalkeeper Petr Cech also remains sidelined for the West Ham game, but Alex Oxlade-Chamberlain and Aaron Ramsey could both be back after missing the Man City game with minor injuries.

"They have a test today and we'll see if they can be involved. I think there's a good chance that they're back in the squad," Wenger said.

Laurent Koscielny had to be substituted at half-time during the draw with Manchester City. Catherine Ivill - AMA/Getty Images

Wenger once again brushed off questions about his own future, refusing to say when he plans to announce whether he plans to renew his contract after this season.

"I have answered that question many times. I can understand that you ask again. Don't worry, you will get that soon," he said.

Wenger also bristled at questions about the future of Alexis Sanchez, who has yet to agree to a contract extension and has been linked with a move away from Arsenal this summer. French radio station RMC reported on Tuesday that the Chile striker has already opened talks with both Paris Saint-Germain and Chelsea about a possible transfer.

Arsenal have shelved talks with both Sanchez and Mesut Ozil until the summer, and Wenger insisted there was no reason to worry about their situation at this point.

"He has one-and-a-half years of contract, I don't see what suddenly all that debate is about," Wenger said. "We are professional football people, I don't understand. Our job is to perform as long as we are somewhere. When I sign a contract I commit until the last day of my contract, and that is what it is to be professional. So I do not understand this kind of anxiety one-and-a-half years before the end of contracts. It's absolutely denying what a professional guy is about."

Wenger has faced fan protests outside the Emirates before recent home games, and a few fans even stood outside the club's training ground on Sunday holding a sign reading "#WengerOut, #AlexisIn." One of them was dressed up as Wenger holding up a "4th Place Trophy" -- mocking the manager's habit of listing the team's annual top-four finishes as an achievement.

Arsenal are in real danger of finishing outside the top four for the first time during Wenger's 21-year reign as they sit sixth in the standings with 10 games to play, but he insisted it's still "perfectly possible" to keep that streak alive.

"Certainly for 20 years I have done it and it looked always like it's nothing," he said. "Suddenly it becomes important, so I am quite pleased that people realise that it's not as easy as it looks. And if you listen to [Pep] Guardiola, he said the other day that to achieve the top four in England is a trophy because it's so difficult.

"Of course we have a difficult task in front of us, but I am happy as well that people realise suddenly that it's not as easy as it looked always."