Mohamed Elneny's World Cup hopes suffered a potential blow on Sunday as the Egypt star was forced off injured in Arsenal's Premier League clash with West Ham.
The midfielder appeared to sustain an ankle injury in a challenge with Mark Noble and, after prolonged treatment on the field, he was taken off on a stretcher with his leg in a brace.
Elneny – who has 57 caps for his country – looked in significant discomfort as he was replaced by Ainsley Maitland-Niles at Emirates Stadium.
Of immediate concern for the 25-year-old will be Thursday's Europa League semi-final first leg with Atletico Madrid, but his ambitions to feature in Russia may also take a hit.
Elneny, who signed a new long-term contract in March, was only cleared to play after having his red card against Southampton overturned.
Hector Cuper's men are in Group A alongside Uruguay, Saudi Arabia and the tournament hosts.