Marcus Rashford
Rashford scored the only goal of the game before injury struck. Getty

Manchester United are sweating over another injury after Marcus Rashford limped out of their Champions League victory over Benfica with a knee problem.

Rashford, 19, scored the only goal of Wednesday's (18 October) match during a bright second-half performance from the youngster, who was given the nod over Anthony Martial on the left of attack.

After testing Benfica's 18-year-old goalkeeper Mile Svilar from a series of corners, the United striker caught out the Champions League debutant with a 35-yard free kick which the goalkeeper carried into his own net.

Just 12 minutes later, however, his evening was brought to a premature end when he fell to the ground in real discomfort, immediately removing the shin pad on his left leg before limping off to be replaced by Martial.

Mourinho was quizzed on the incident in his post-match interview, telling BT Sport: "It is something in knee, I thought it was cramp or a bit of fatigue but it is something he felt in his knee. I hope nothing important."

The United striker will likely undergo scans on Thursday to determine the extent of the injury.

United have endured rotten luck with injuries in the opening months of the 2017-18 season. The club remain without three midfield options in Paul Pogba, Marouane Fellaini and Michael Carrick with defender Eric Bailly recently joining the injured list after returning from international duty with an unspecified knock.

Phil Jones is the latest victim. The 25-year-old made the trip to Lisbon for Wednesday night's game and was expected to retain his place at the heart of defence after his solid performance in the goalless draw with Liverpool. But in his pre-match interview with BT Sport, Mourinho revealed the former Blackburn Rovers starlet had picked up an injury which paved the way for Victor Lindelof to start against his former club.

United are yet to clarify the nature of Jones' injury but note on their official website the defender picked up the problem while on international duty with England last week, managing to play against Liverpool despite the knock.

Mourinho also remains without Marcos Rojo and Zlatan Ibrahimovic as they continue their recoveries from long-term knee injuries.