Manchester United are facing growing midfield injury problems amid fears that Anderson could be sidelined for up to two months after suffering suspected cartilage damage during Saturday's FA Cup win over Crawley Town.
The Brazilian midfielder, who was replaced by Wayne Rooney at half-time against Crawley, left United's training ground on crutches yesterday after being assessed by the club's medical staff.
Anderson was treated on Sunday after complaining of discomfort in the knee during the fifth-round tie against the non-league club, with the initial prognosis suggesting that the 22-year-old could be out of action until mid-April.
Surgery remains an option, but United hope Anderson will be able to return ahead of schedule if the injury does not require an operation. He will be reassessed later this week.
Anderson had already been ruled out of tomorrow's Champions League first leg last-16 tie against Marseille due to the injury, but his absence will leave manager Alex Ferguson without four first-team midfielders at a crucial stage of the season.
Ji-Sung Park and Antonio Valencia are unlikely to return before mid-March due to hamstring and ankle injuries respectively, while Owen Hargreaves continues to show no sign of a return from long-term injury.
United travel to Marseille today having confirmed that defender Patrice Evra has signed a new contract committing him to Old Trafford until June 2014.
The 29-year-old had been linked with a summer move to Real Madrid amid uncertainty over his readiness to extend his deal beyond June 2012.
Evra said: "Ever since I arrived at United, it's been a dream come true playing here. I've won a lot in the last five years, but I want to win more."
Meanwhile, Gabriel Heinze, Marseille's Argentine full-back who left United in August 2007 after losing his place to Evra, is set to face his former club for the first time tomorrow. (© Daily Telegraph, London)