Wayne Rooney scored the winner but suffered a hamstring injury in a 1-0 victory over Wigan Athletic that moved Manchester United up to second in the Premier League on Wednesday.
The England striker netted after just 54 seconds at Old Trafford but hobbled off soon after scoring and will be sidelined for at least three weeks, manager Alex Ferguson said.
"Unfortunately we lost Wayne Rooney and Carlos Tevez came on and did fantastically for us then he got injured. It was a test of our character for the last half hour because it was an absolutely brilliant performance by Wigan," Ferguson told Sky Sports News.
United, who have 44 points and a game in hand, will go top if they beat Bolton Wanderers on Saturday as leaders Liverpool, who have 46, do not play until they host Everton in the Merseyside derby on Monday.
Wigan, coached by former United favourite Steve Bruce, remain in seventh place. Shortly before kickoff they rejected a 10 million pounds bid from Tottenham Hotspur for Honduras midfielder Wilson Palacios.
"When the big boys start circling and coming and nicking your players, unfortunately if they pay enough they are always going to get their own way," Bruce said.
Rooney's first minute strike came after a good run and cross from newly-crowned FIFA World Player of the Year Cristiano Ronaldo although that was virtually Rooney's last contribution as he limped off eight minutes later.
He was replaced by Carlos Tevez who had a great chance to double United's lead soon after coming on but lost control of the ball after rounding Wigan keeper Chris Kirkland.
Wigan battled hard but failed to score against a United side who have now gone nine Premier League games without conceding a goal.
They tested goalkeeper Edwin van der Sar with a volley from Maynor Figueroa and almost drew level with nine minutes left when Antonio Valencia's drive just went over the bar.