Diaby joins Arsenal injury list
Midfielder Diaby damaged his ankle in the Premier League victory over Bolton Wanderers on Saturday while central defender Vermaelen is still nursing a knock to his Achilles tendon sustained while playing for Belgium last week.
"Diaby is out with an ankle problem following the tackle from (Bolton defender) Paul Robinson and I do not know for how long," manager Arsene Wenger told a news conference on Tuesday.
"He will not play tomorrow and certainly not at the weekend," Wenger said.
"Thomas Vermaelen is out as well with an Achilles problem coming back from Belgium, so we do not have him either.
"We have Walcott, Van Persie, Bendtner and Ramsey already out. Now Vermaelen and Diaby, so that is quite a good team out."
Theo Walcott was injured while playing for England and faces a six-week lay-off, as does fellow striker Robin Van Persie.
Nicklas Bendtner has been struggling with a groin injury.