Ole Gunnar Solskjaer has been left sweating over the fitness of Eric Bailly after the defender was injured playing for the Ivory Coast.
The Manchester United centre-back was involved in a nasty collision during the African Cup of Nations qualifier with Rwanda on Saturday and had to be substituted.
There were fears Bailly had swallowed his tongue but he was able to walk off the pitch to undergo further tests.
Ivory Coast won the game 3-0 to move level with Guinea at the top Group H.
Solskjaer will be hoping the Ivorian will be fit to face Watford on Saturday after a flurry of injuries during the international break.
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Marcus Rashford, Jesse Lingard and Luke Shaw withdrew from the England squad ahead of the double-header against Czech Republic and Montenegro.
Romelu Lukaku, Anthony Martial and Nemanja Matic also picked up injuries and United face a race against time to get their crocked stars back in time to take on the Hornets.
The Red Devils are two points behind fourth-place Arsenal in the battle for the Champions League spots.
Solskjaer's side also have a European quarter-final with Barcelona on the horizon.
