Danny Welbeck left the Etihad Stadium in a protective boot on Monday, compounding Manchester United's derby misery.
The Red Devils striker was left nursing a knock to his ankle as United suffered a 1-0 defeat by arch-rivals Manchester City to slip from the Premier League summit.
Welbeck was drafted into the action as a second-half substitute, as the visitors chased an equaliser, and was caught by a hefty challenge from Nigel de Jong.
The incident sparked a furious touchline row between Sir Alex Ferguson and Roberto Mancini, with the two managers having to be kept apart by their respective coaching staff.
Ferguson later accused Mancini of 'badgering' the match officials and trying to influence decisions.
The Scot would appear to have every right to feel aggrieved, with it possible that Welbeck could now be forced to sit out United's final two games of the season.
That would prevent him from playing any part in their efforts to pip City to the post and successfully defend their top-flight crown.
Welbeck's injury is also concerning for England, with Euro 2012 fast approaching.
The 21-year-old, who has netted 12 goals in all competitions this season, was expected to form part of the Three Lions' squad for this summer's European Championship - with his domestic strike partnership with Wayne Rooney likely to work in his favour.