Manchester United manager Sir Alex Ferguson says striker Javier Hernandez will be out of action for two weeks.
The Mexico forward, 23, was injured during training in New Jersey ahead of the friendly with the MLS All-Stars and spent Tuesday night in hospital suffering from "mild concussion".
"He got concussion in training and we dealt with that," said Ferguson on the club's tour of the United States.
"We took him to hospital, he had a scan, it was all clear."
Ferguson added: "He is back in the hotel. He is in his room and will be out for a couple of weeks.
"He would never have been available for Barcelona [friendly on 30 July] anyway because he has just come back from his break after the Gold Cup.
"He will travel with us though. He is OK for that."
Following the match against Barcelona, United then face New York Cosmos on 5 August before the Community Shield match against Manchester City on 7 August.
The Premier League champions open their campaign for the new season on 14 August, away at West Brom.
Hernandez, who has 29 international caps, scored 13 Premier League goals in his first season after signing from Mexican side Chivas de Guadalajara for £7m last season.
The Red Devils beat the MLS All-Stars side, which included former United midfielder David Beckham, 4-0 thanks to goals from Anderson, Ji-Sung Park, Dimitar Berbatov and Danny Welbeck.
United will conclude their US tour on Saturday against European champions Barca in Washington.