The attacker, who did not start against Manchester United at the weekend, has joined the growing list of absentees for the trip to Germany after falling ill on Sunday night.
Arsenal forward Theo Walcott is doubtful for Tuesday's Champions League clash with Schalke due to coming down with an illness, according to manager Arsene Wenger.
The Gunners boss is preparing to be without the England international, who is being given until the morning of the game to prove his fitness, while Aaron Ramsey has been confirmed as absent due to a groin strain, with Johan Djourou replacing the midfielder in the squad.
"[Walcott] has been sick overnight [and] didn't practice today [Monday] so we have to see how he is on Tuesday morning," Wenger told reporters.
Wenger, however, have some positive news with the announcement that Jack Wilshere is likely to start against the Bundesliga side.
"I think I will play [Wilshere]," Wenger said. "Then we have a block of three games and maybe the fact that he gets a period of recovering will be just right for him. He gets better in every game."
Wenger has made it clear that the team must get back to winning ways as soon as possible, and has labelled the trip to Germany as the perfect opportunity to bounce back from their recent run of bad form.
"[Our form] is a concern, because we had a very promising start and of course we have gone through a difficult spell," Wenger said. "We want to respond to that and rectify that very quickly because it is not only the fact we lost the [Manchester United] game but the way we lost it.
"In terms of the group, the fact that we lost against Schalke means it is important that we win [in Germany] and finish the job well. We are still in a strong position in this group but of course we want to come out with a good result."
The French coach has insisted that his team have put their defeat to Manchester United behind them, and are looking to respond in the right way to take back the initiative in Group B.
"We have analyzed it, watched it and spoken about it," added Wenger. "We know that we didn't perform as well as expected. There is only one way to respond to that and that is to come out with a good performance tomorrow night."