Alexis Sanchez was injured in a freak incident during Manchester United's defeat by Paris Saint-Germain - colliding with a linesman while he was warming up.
Chile star Sanchez is now battling to be fit for Monday's FA Cup tie against Chelsea at Stamford Bridge, with Anthony Martial and Jesse Lingard already serious doubts for the fifth-round clash.
Sanchez was preparing to come on for Lingard, who had strained his left hamstring towards the end of the first half in the 2-0 Champions League defeat.
Alexis Sanchez was injured in a freak incident during Man United's loss to Paris Saint-Germain
However, the United substitute became distracted by the match action as he jogged along the touchline and ran straight into Italian linesman Fabiano Preti.