The Ecuadorian limped off early on in the game at the Levi's Stadium, with United yet to make any public announcement as to the extent of the damage.
The club will be hoping it is nothing serious, with new signing Diogo Dalot out until September after knee suregery and Matteo Darmian expected to leave the club this summer.
Darmian is the only fit right-back in the United squad at present, but he is expected to return to Serie A before the transfer deadline, with Napoli among his admirers.
United get their Premier League campaign underway with a home game against Leicester on August 10, giving Valencia a little over two weeks to return to fitness.
Valencia is expecting to be named United captain this season following the retirement of Michael Carrick.