Manchester United's Antonio Valencia limps off injured in friendly

SANTA CLARA, Calif. -- Jose Mourinho is facing his first injury scare of Manchester United's summer tour after Antonio Valencia limped off against San Jose Earthquakes.

Valencia, 32, lasted just seven minutes of United's second preseason game at Levi's Stadium on Sunday.

The right-back hobbled off with looked like a calf injury and went straight down the tunnel. Matteo Darmian came on his place.

It will be a worry for Mourinho who is already short of players after the World Cup in Russia.

The United boss had already revealed his plan to start the Premier League season with a back four of Valencia, Luke Shaw, Eric Bailly and Chris Smalling.

New signing Diogo Dalot, 19, is out until September with a knee injury while Phil Jones, Ashley Young, Marcos Rojo and Victor Lindelof are on holiday after the World Cup.

Valencia's injury could affect United's stance on Darmian. Sources have told ESPN FC the club are willing to listen to offers for the Italian and have held talks with Juventus.

Inter Milan and Napoli are also interested but Mourinho will not be keen to lose a full-back if Valencia is ruled out for a significant length of time.