Arsenal's joy at a 4-1 Carling Cup derby victory at Tottenham Hotspur was tempered by left-back Kieran Gibbs suffering a foot injury during extra-time at White Hart Lane.
The 20-year-old England international suffered a metatarsal problem last season and manager Arsene Wenger fears that the fresh setback could be a similar injury.
He said:"We have to check, that is the only disappointment of the night, because Gibbs had a very good game.
"We hope we do not get bad news tomorrow morning.
"It is a metatarsal again, it is the one next to the one he had broken, the second one, so we hope we have good news, because that would be a massive blow to us."
Meanwhile, Wenger defended his approach to the competition, having often fielded a second-string side.
He added:"We have got a few reproaches that we did not take the competition seriously, it was a derby and to go out straight away for us would be difficult.
"We have a momentum going and it was important not to interrupt it, also some players needed competition.
"If everybody is fit, I can go as well for this competition."