Shaw has had some issues to overcome this term and struggled for game time, although the England international had managed to force his way back into Mourinho's plans in recent weeks.

However, the United boss has confirmed Sunday's start against Swansea was his 19th and final appearance of a difficult campaign, having been forced off after just nine minutes.

Press Association Sport understands the left-back was due to see a specialist after scans showed ligament damage in his left foot, which Mourinho says will bring his campaign to a premature end.

"Luke Shaw is injured and it is an important injury obviously," Mourinho said ahead of the Europa League semi-final first leg at Celta Vigo.

"But we are still waiting for one more medical opinion for the medical department to decide what to do.

"But it doesn't matter what, he is out for the season. That is confirmed."

Shaw joins Zlatan Ibrahimovic, Marcos Rojo and Tim Fosu-Mensah on the sidelines, although Paul Pogba, Chris Smalling and Phil Jones return to the fold in Spain.

Eric Bailly is "ready to play" after being forced with a muscle problem against Swansea, while Juan Mata is available to face Celta after returning to the bench on Sunday following a groin injury.