Declan Rice was likely injured during Arsenal 5-0 win over Crystal Palace.
Shortly before Jorginho replaced him the Englishman was heard to say hammy which could mean he suffered a hamstring injury.
Rice started all of Arsenal Premier League games after joining West Ham in the summer. He also never missed a Champions League match.
His injury will be a big headache for Mikel Arteta who lacks options in midfield.
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