Manchester United left-back Luke Shaw has been ruled out for four weeks with a hamstring injury, the club have announced.
Shaw, who joined the Red Devils from Southampton in June for £27million, is expected to miss United's first three Barclays Premier League games, including their opener against Swansea on Saturday.
A tweet from Manchester United's official Twitter account said: "Luke Shaw has a hamstring injury and is expected to be out for around four weeks."
The 19-year-old, who became the world's most expensive teenage footballer when he made the move to Old Trafford, could also miss further Premier League games against Sunderland and Burnley.
A statement on Manchester United's official website read: "Luke Shaw has suffered a hamstring injury and will miss the opening game of the season against Swansea City on Saturday.
"The England international, a summer signing from Southampton, is likely to be sidelined for around four weeks.
"Shaw sat out the friendly victory against Valencia at Old Trafford due to the problem and faces a wait before making his competitive debut for the club."
Shaw made his United debut against LA Galaxy in July during their summer tour of North America.
Earlier on Wednesday, the Red Devils confirmed that Shaw had been given the number three shirt for the forthcoming season, after it had been vacated by Patrice Evra's departure for Juventus.