Sir Alex Ferguson has challenged his Manchester United players to dislodge Liverpool from the top of the Barclays Premier League table by Saturday evening, despite warning that the match against Wigan Athletic at Old Trafford this evening has become more perilous for the champions on the back of Sunday's emphatic defeat of Chelsea.

With Liverpool, the leaders, inactive until Monday's game at home to Everton, victories against Wigan and Bolton Wanderers in the next four days will take United to the top of the table for the first time this season. However, Ferguson, the United manager, has warned against complacency creeping into his squad in the wake of their 3-0 win against Luiz Felipe Scolari's team.

Wigan will arrive at Old Trafford having lost all six previous league encounters against United. But a run of six victories from their past seven league games has lifted Wigan into seventh place in the Premier League and Ferguson believes that United face a stern test of their credentials given the visiting team's form and soaring expectancy at Old Trafford fuelled by the victory against Chelsea. “There is no case to say that the hard work has been done by beating Chelsea,” he said. “The game against Wigan is harder for us now because it's one of our games in hand and we have to win.

“On the back of the Chelsea game, people will expect the same level of performance, but that was a very high level and Chelsea worked amazingly hard.

“Wigan have done fantastically well by getting six wins out of their last seven. Their record is very, very good, but we will freshen things up for the game and make a few changes; changes that we hope will bring about the right result.”

With the title race descending into a psychological battle between Ferguson and Rafael Benítez, the Liverpool manager, United could land a potentially telling blow by securing the top spot before Monday's Merseyside derby. Ferguson believes that seizing pole position by the time the final whistle is blown at the Reebok Stadium on Saturday is the sole objective for United. “We certainly hope to be top by Sunday morning, but, first of all, we have a big game against Wigan,” he said. “We have to get this one done and then reflect on what we have to do at Bolton.

“The games in hand have been a handicap because it's not easy to make them up, but we are getting one of them out of the way now. The next one [against Fulham at Old Trafford] is a month away. But until we play the two games in hand, we can't judge where we are because we are still chasing the teams in front.”

United will be without Patrice Evra, the left back, and Rio Ferdinand, the central defender, against Wigan after Ferguson revealed the extent of the pair's injuries. John O'Shea and Jonny Evans are likely to deputise. “Evra will be out for three weeks minimum, and maybe four, but it shouldn't be any more than that,” Ferguson said. “He went over on his foot in the Chelsea game and has done a little ligament [damage], so we need to get the swelling down and that will take about seven to ten days.

“Rio has been to a specialist and there are no major problems with his back, but he won't be involved against Wigan. We are giving him a series of exercises, but he should be OK and we hope he'll be back for the FA Cup tie against Spurs on January 24.”