Manchester United boss Sir Alex Ferguson has confirmed that Anderson is facing a three-week spell on the sidelines after suffering a hamstring injury.
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Anderson, 24, limped off during last Saturday's win at Reading, having scored United's first goal of the match.
The injury comes at an unfortunate time for the Brazil midfielder, who has just started successive Premier League games for the first time this season.
"It is a hamstring,'' Ferguson told MUTV. "It will be three or four weeks. It is not serious but it is a hamstring.''
Starting with this Sunday's Manchester derby away to Manchester City, United face six Premier League games in a hectic 23-day period and it seems likely that Anderson will miss all of those matches, with a return for the FA Cup third-round trip to West Ham on January 5 a possibility.