Arsenal manager Arsene Wenger is concerned by the injury Aaron Ramsey suffered in the 4-0 FA Cup win at Hull.
Midfielder Ramsey, set to play a key role for Wales at Euro 2016 this summer, was replaced 16 minutes after coming on as a second-half substitute.
Arsenal have Laurent Koscielny out and fellow centre-backs Per Mertesacker and Gabriel also picked up injuries.
"The most serious looks to be Ramsey," said Wenger. "I think it's a thigh strain."
Mertesacker was involved in a clash of heads with Hull midfielder Nick Powell as holders Arsenal won the fifth-round replay to book a home quarter-final against Watford on Sunday.
"Mertesacker is just a cut on his eye," added Wenger. "That looks to be very short term. Gabriel is a hamstring."
Two goals each from France striker Olivier Giroud and England forward Theo Walcott secured Arsenal's first win in six games.
That run has included a 2-0 Champions League last-16 first-leg defeat by Barcelona and Premier League losses to Manchester United and Swansea.
Against Hull, some Gunners fans held up a banner reading "Arsene, thanks for the memories but it's time to say goodbye".
Wenger said: "There's nothing disappointing for me, I do my job. Look at the history of the club and you will see that I have nothing to be scared of."