Manchester United manager Jose Mourinho has issued a rallying call to defender Luke Shaw, urging the young left-back to keep working hard as he attempts to reclaim a place in the side’s starting XI.

Shaw has fallen out of favour under the United boss, with injury and an alleged lack of mental resilience seemingly keeping the 21-year-old out of the Portuguese’s team.

Prior to withdrawing himself from selection for United’s 3-1 victory at Swansea last November - prompting Mourinho to question his dedication to the side - the defender had featured in seven games for the Old Trafford club.

His last league performance came against Burnley in October and he has not played a single minute since.

Shaw’s continued absence has been a source of puzzlement for many United fans but Mourinho insists he must keep fighting to prove his worth to the side.

"The only thing I can say is that Luke is working well," he said.

"I don't have any problem and he's working well. He's fighting hard, there is no problem with him.

"He has to work and wait."

Explaining why Matteo Darmian had been picked to provide defensive cover on the bench ahead of Shaw for Saturday’s 2-0 win over Watford, Mourinho added: "But I want one defender on the bench and the defender on the bench is somebody who can play more than one position.

"And Darmian can play left-back, right-back and would be an emergency central defender for us, so my choice was Darmian.”

United’s upcoming congested fixture list could work in Shaw’s favour as they continue to battle in four competions.

The 20-time English champions host St Etienne on Thursday in the last 32 of the Europa League in the first of four games in 11 days for Mourinho’s side.

Luke Shaw has not played a single minute in the league since October (Getty)

United then travel to Blackburn in the FA Cup on Sunday, before heading to France on February 22 for the return leg against St Etienne.