Jose Mourinho has revealed that Manchester United forward Anthony Martial is suffering from a knee injury that puts his FA Cup final participation in doubt.

The 22-year-old was due to start the Red Devils' meeting with Watford on Sunday, six days ahead of the Wembley showdown against Chelsea.

Martial was absent from the matchday squad after picking up an injury in training on Friday, however, and is now in a race against time to return to fitness for next weekend.

Mourinho is expected to have Romelu Lukaku back for the match, though, following a two-week spell on the sidelines since damaging his ankle against Arsenal.

"[Martial's injured]. He was injured in Friday's training session, yesterday couldn't train," Mourinho told reporters. "He had treatment in the morning at the training round and he stayed away.

"I don't know [when he will return]. I know that Romelu will be back for Tuesday because he's in the last week [of rehabilitation] and we have to see but Anthony I have no more."

Martial has started fewer than half of United's 38 Premier League games this season.