ENGLAND (REUTERS) - Manchester United manager Jose Mourinho has asked winger Anthony Martial to deliver more consistent performances after the French international forward dazzled in a pre-season victory over Real Madrid on Sunday.

Martial produced an impressive performance, including a fine run to set up United's opening goal for Jesse Lingard before United defeated Madrid on penalties at the Levi's Stadium in Santa Clara.

Mourinho said he saw an improvement in Martial's work ethic in training ahead of the new campaign, but the 21-year-old will need to do more on the pitch to impress him.

"Obviously we want more consistency in his talent," Mourinho told reporters.

"I think today was positive for him, that's why I left him for 90 minutes on the pitch.

"He was enjoying it and trying things, it's important to try things in these friendly matches, so it's good for Anthony and his confidence.

"I can say he is training better than before, he's working harder than before. It's just a question to bring his talent more in a consistent way."

United face Barcelona on Wednesday in Washington DC with a doubt over the fitness of Spanish international midfielder Ander Herrera, who was substituted after suffering a knock in the second half.

"It must at least be very painful because for Ander to come off, it has to be very painful," the Portuguese added.

"I want to wait and see what it is... it was in front of the bench, it was a bad contact. Maybe it is his ribs but I don't know."

Mourinho is already without defenders Marcos Rojo, Luke Shaw and winger Ashley Young ahead of the season after the trio suffered long-term injuries at the end of last campaign.

United kick off their Premier League campaign at Old Trafford against West Ham on Aug 13.