Wayne Rooney may miss the start of the English Premier League Season after he injured a hamstring while on Manchester United's tour of the Far East.
United said on Friday they expected the striker to be sidelined for a month after he was injured in a training session before a friendly against a Thailand All Stars team in Bangkok.
The incident comes amid mounting speculation about the 27-year-old's future, after he reportedly asked for a transfer at the end of last season.
New United manager David Moyes said Rooney would not leave the club.
"Unless I was speaking double Dutch, I've said that Wayne Rooney is not for sale," Moyes said at a media conference on Friday.
Chelsea manager Jose Mourinho added to the speculation on Friday when he said that he admired Rooney "very, very much", but he stopped short of saying he hoped to sign the unsettled star.
Rooney was sent home from Bangkok after spending only 16 hours in the Thai Capital.
Moyes told Manchester United TV from the Bangkok that Rooney had been sent home because there was no point in risking him on the tour after his hamstring tightened up in England.
"After the long flight, we decided we'd get him tested and scanned and have a look at things and there is just a small grade one injury there," the Scot said.
"He didn't train yesterday. We won't take any chances. There is no point in taking him any further round the world so we've sent him back."
Rooney played down the injury.
"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,'' Rooney posted on his Facebook page.
The injury prevents Moyes from experimenting with different forward combinations in framing a gameplan for the post-Alex Ferguson era.
United was already short of options up front for the Thailand game, with Rooney's fellow striker Robin van Persie on an extended break. Van Persie is due to join the team in Australia for the next leg of their preseason tour.
The absence of Rooney and van Persie means Danny Welbeck is likely to be the front man for the game against Thailand All Stars on Saturday evening at the Rajamangala National Stadium.
Chris Smalling, Ashley Young and Shinji Kagawa, who will only appear in the last Asian stop in Japan, are also out of the Bangkok game.