The England international will miss out on the club's first games under the stewardship of David Moyes, and is expected to be sidelined for around a month - ruling him out of the club's meeting with the cream of the A-League at Sydney's ANZ Stadium.
 
"Following a scan this evening on a hamstring injury sustained in training, it has been decided Wayne Rooney should return home immediately for further assessment and rehabilitation," United said in a statement.
 
However, Rooney could still be fit in time to feature in United's first game of the new Premier League campaign - a trip to face Swansea City at the Liberty Stadium on August 17.
 
Rooney's future at Old Trafford remains in doubt after former manager Alex Ferguson revealed the player had handed in a transfer request at the end of the 2012/13 season.
 
The 27-year-old's representatives immediately moved to deny those claims, but suggestions of an uneasy relationship between Moyes and Rooney have only served to increase rumours of a potential departure.
 
United will kick off their pre-season schedule by taking on the Singha All-Stars in Bangkok on Saturday.