Arsenal fear Kieran Tierney could miss the rest of the season.
The Scotland left-back was absent for Monday's 3-0 loss to Crystal Palace, a match in which Thomas Partey was also injured.
Speaking after the game, manager Mikel Arteta admitted Tierney was in trouble with a knee injury.
"He is seeing the specialist tomorrow and we will know more the extent of the injury," said Arteta.
"But the feeling that he had it wasn't really positive and what the scans showed either, but we have to wait and see what happens."
The London Evening Standard reports that there are fears Tierney could be sidelined for Arsenal's remaining nine Premier League matches.
The loss to Palace leaves Arsenal level with fourth-placed Tottenham on points, although they have a game in hand over Spurs.
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