Theo Walcott and Nicklas Bendtner are back in Arsenal's squad for Sunday's clash against Blackburn but Eduardo has been ruled out with a thigh injury.
England winger Walcott returned from a side strain, while Bendtner is fit following a car crash earlier in the week.
"Unfortunately we lost Eduardo after he came on [against Olympiacos]," said Arsenal boss Arsene Wenger on Arsenal TV Online.
"It was a gamble to play him and unfortunately his muscle injury got worse. He will be out. It is the same thigh muscle and has recurred a few times now. But Walcott and Bendtner are available."
Manuel Almunia has been missing with a chest infection since the defeat at Manchester City on September 12 and may not be ready to return.
"Manuel Almunia is not far," said Wenger. "I will assess him Friday or Saturday but he looks unlikely to be ready."
Meanwhile, Walcott insists his belief in ending the club's trophy drought led him to signing a new contract.
Walcott agreed new terms towards the end of last season and is determined to win his first silverware since arriving from Southampton in 2006, the season after Arsenal lifted their last cup.
Walcott said: "I signed because I have got a lot of belief in the club and in the team.
"We have gained a lot of experience over the last few years and although we haven't won any trophies, I think that will change this year.
"If you want to win trophies, it is important to keep the group together - Manchester United are a good example of that.
"This summer, Robin (Van Persie), Nicklas, Kieran [Gibbs] and a few others signed new contracts and I firmly believe we can win things here. We've also added to the squad with Thomas Vermaelen and for me he is a top lad - he's our top scorer too.
"He has settled in really well and he's such a nice guy. I have trained with him a few times now and he's a very tough competitor.
"He has got an absolutely great leap on him too - he will win a header against anyone. I reckon he would beat Peter Crouch in the air."Reuse content