Arsenal have been hit by a further blow after Aaron Ramsey limped off in the early stages of their clash against Watford.
The Wales international was replaced by Alex Oxlade-Chamberlain, but his potential absence could cause Arsene Wenger a headache in the coming weeks.
Granit Xhaka remains out with a suspension while Mohamed Elneny is away at the African Cup of Nations, where he has picked up an injury playing for Egypt.
Santi Cazorla is on the sidelines with a long-term achilles injury which leaves the inexperienced option of Ainsley Maitland-Niles or the versatile Oxlade-Chamberlain as options for Wenger to partner Francis Coquelin.
Wenger's side face Chelsea on Saturday in a crucial Premier League clash and will be hoping that they have Ramsey fully fit for the encounter at Stamford Bridge.