Alex Ferguson said Manchester United were "halfway" to the Premier League title after Robin van Persie scored late on to seal a 2-0 win over West Bromwich Albion.

United go into Tuesday's visit to Wigan Athletic leading the Premier League by seven points from defending champions Manchester City, and with van Persie having scored 33 club goals for Arsenal and Ferguson's team in the year 2012.

His last-minute effort in the 2-0 win against West Brom, adding to an early Gareth McAuley own goal, was his 14th Premier League strike since moving to Old Trafford in the close season and his 17th for United in all competitions.

After scoring his goal towards the end of Saturday's game, van Persie revealed a T-shirt bearing the words 'RIP Tchuna', in tribute to a personal friend who had passed away on the eve of the game.

Ferguson certainly appreciated the efforts of his forward and the United manager believes that United are halfway towards completing their goal of wrestling the league title from City's grip.

"He (van Persie) changed the game for us," said Ferguson. "When I brought him and Paul Scholes on, they settled the game down for us.

"It (van Persie's goal) is fantastic. He is a fantastic player. He came on and changed the game for us.

"Every time the ball came up to him, he got hold of it. He turned on them. They were having to go back to their box all the time. He has done well.

"We're in a good position. We're halfway there. We've a game on Tuesday away from home at Wigan and we've got a few players to freshen it up. We'll look forward to the next game and try and win it.

"It's important, though, that we do not sit looking at the league table, admiring our position, positive though it is, because we would soon get a rude awakening.

"Congratulating ourselves on our Premier League lead doesn't mean a thing to me. It's winning the next game that counts."

Given his team's defensive problems of late, Ferguson was arguably even more content with the efforts of his defenders, who kept just their fourth clean sheet of the season in the Premier League.

"We defended their crosses very well," said Ferguson. "They kept pumping it in and we had to make sure we were competing for all the crosses, which we did very well.

"It will be a hard game on Tuesday. Wigan have had a great result today (a 3-0 win at Aston Villa on Saturday).

"Hopefully we can freshen up again. Possibly Phil Jones will be ready. Rafael will be ready. We rested Javier Hernandez today, Ryan (Giggs) and Paul (Scholes). We have enough freshness to bring in on Tuesday."

Steve Clarke, the West Brom manager, was disappointed by the margin of defeat and felt the sodden Old Trafford playing surface -- which required two pre-match pitch inspections before being declared playable -- did not help his team.

"The scoreline didn't reflect how well we played, particularly in the second half," said Clark.

"The pitch was dreadful and trying to play through the middle was something we got caught out by.

"But you don't look for games to be called off. We used to play on pitches like that all the time. There was no reason to call that game off."

Clarke's club have been one of the big surprises of the Premier League season, although the manager refuses to be carried away by his team's impressive first half of the campaign.

"It's difficult for a club like us to look too far ahead," he said. "Like our fans keep singing, we know what we are.

"We know what we're trying to be and what we're trying to build as a team and for us to look too far ahead would be wrong.

"We've got Fulham at home in two days' time and the first target for us, like most teams in the league, is to get to the 40-point mark so we can say we're safe. When we reach that, we will re-assess and set ourselves another target."