Manchester United have announced that Wayne Rooney has left the club's pre-season tour of the Far East after sustaining a hamstring injury.
United landed in Bangkok on Thursday morning, heading to their hotel before beginning their first training session, during which Rooney picked up the problem.
He is set to be out of contention for a month.
A statement on United's official website read: "Following a scan this evening on a hamstring injury sustained in training, it has been decided that Wayne Rooney should return home immediately for further assessment and rehabilitation.
"It is anticipated he will be unavailable for selection for a month."
Rooney, though, played down the injury as he expressed his disappointment via Facebook: "Gutted to have picked up a niggling injury especially as training was going so well, heading back to Manchester to have it assessed fully but early indications are nothing to worry about."
United play Wigan Athletic in the Community Shield on August 11 before beginning the defence of their Premier League trophy at Swansea City on August 17.
New United boss David Moyes had stressed again this week that Rooney was not for sale and that the forward was in good shape ahead of the new campaign.
"I will say he is training great," he told talkSPORT on Wednesday. "They are telling me it is the best shape they have seen him in for a long time. From that point of view I am taking it as a positive and I am going to try and get the best Wayne Rooney I possibly can."