Sir Alex Ferguson has warned that Manchester United face a tougher challenge against in-form Wigan than that posed by Chelsea at Old Trafford during Sunday's 3-0 victory over Luiz Felipe Scolari's team. Champions United claim top spot in the Premier League for the first time this season if they defeat Wigan at home on Wednesday and then collect three points from the game against Bolton at the Reebok on Saturday.

But Wigan, managed by former United captain Steve Bruce, head for Manchester having won six of their last seven league games, including Sunday's dramatic injury-time victory over Spurs at the JJB Stadium. And with few expecting anything other than a straightforward United victory, Ferguson has insisted that Wigan will be more difficult to overcome than title rivals Chelsea.

Ferguson said: "There is no case whatsoever that the hard work has been done by beating Chelsea. This is a harder game for us now. It's one of our games in hand and we have to win this game. Wigan have done fantastically well by getting six wins out of their last seven, but I did think that they would do well this year actually.

"They got off to a disappointing start, which was unexpected because I thought they would get off to a flyer, but they have recovered now and their record is very, very good. On the back of the Chelsea game, though, people will expect that same level of performance, but that was a very high level performance and, having looked at the stats again, Chelsea worked amazingly hard, so that shows you the level that we got to.

"But we will freshen things up for the Wigan game and make a few changes, changes that we hope will bring about the right result." Ferguson admits United are determined to take advantage of their next two games by reclaiming top spot ahead of Liverpool's Anfield clash with Everton on Monday.

He said: "We certainly hope to be top by Sunday morning. That's our aim, but it's a big game against Wigan. We have to get this one done and then reflect on what we have to do against Bolton. The games have 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 is a month away, but that happens.

"Until we play the two games in hand, we can't judge where we are because we are still chasing the teams in front." Ferguson is set to stick with Irish duo John O'Shea and Jonny Evans in the back four with Rio Ferdinand (back) and Patrice Evra (foot) still missing. French full-back Evra faces a month on the sidelines after being injured against Chelsea, while Ferdinand is battling to return for the FA Cup fourth round clash with Spurs in ten days' time.

Ferguson said: "Evra will be out for three weeks minimum and maybe four. It shouldn't be any more than that. He just went over on his foot and has done the little ligament in his foot, so we need to get the swelling down and that will take about 7-10 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 Spurs game."