Alex Ferguson has hailed Robin van Persie as the missing piece in Manchester United’s title jigsaw as the Premier League leaders bid to extend their lead at the top against Newcastle on Wednesday.

Van Persie has made a superb start to his United career after leaving Arsenal in a 24 million pound move in pre-season and the Dutch forward’s haul of 15 goals has fired Ferguson’s team four points clear of champions Manchester City heading into the hectic Christmas programme.

The 29-year-old’s dynamic displays have added an extra edge to United in the same way that French playmaker Eric Cantona and Portugal forward Cristiano Ronaldo galvanised previous teams in the Ferguson era.

After missing out on the title to City last season, United were in need of a new driving force this term and Ferguson believes van Persie is providing it.“I am reluctant to subscribe to the cult of an individual. But sometimes you find the last piece of the jigsaw,” Ferguson told United’s official matchday programme.

“We did it when we brought Eric Cantona to Old Trafford and he proved to be the right player at the right club at the right time. He became the catalyst and springboard for our surge to success.

“It doesn’t have to be signing someone for a record fee. Cristiano Ronaldo was not a record buy either but he certainly made a difference as he prospered with us to the extent that he came to be regarded by a lot of people as the world’s best player.”

Without van Persie’s goals, United would be eighth and that perhaps explained Ferguson’s fury when Swansea defender Ashley Williams kicked the ball into the Dutchman’s head as he lay prone on the turf during Sunday’s 1-1 draw at the Liberty Stadium.

How Manchester City manager Roberto Mancini must rue van Persie’s decision to snub the champions in favour of joining United.Mancini had hoped to make van Persie the centre-piece of his team as he looked to build on last season’s title triumph, but instead he has had to watch the striker revitalise his club’s arch rivals, while his own strike-force has gone through a barren period.

Sergio Aguero, Carlos Tevez and Edin Dzeko all laboured once more against Reading, the division’s bottom club, on Saturday and it was left to England midfielder Gareth Barry to show them how to do it with a stoppage-time winner.

The good news for Mancini’s side was United’s failure to defeat Swansea 24 hours later, a result which will give fresh impetus to City’s challenge according to defender Kolo Toure.“It’s giving us encouragement because we haven’t played to our best yet,” Toure said ahead of Wednesday’s game at Sunderland.

“Every team knows we are champions. They play 200 percent and that makes it really hard for us. We just keep fighting, keep pushing and we can still be better.”

United and City could be forgiven for regarding the title race as a strictly Manchester affair this season, especially as Chelsea have appeared on the verge of self-destructing at times.

But the Blues finally showed signs of emerging as a serious contender on Sunday thanks to an 8-0 demolition of Aston Villa.That victory left Chelsea 11 points behind United but with a game in hand and interim manager Rafael Benitez refuses to write off the prospect of a title challenge.

“You could see the mentality of the players, even at 6-0 we were pushing and trying to score more,” he said.“The team are attacking as a whole and not just depending on one or two players.“Now we have to sustain this run, keep winning some games and then it will be easier for me to send a message out that we can compete.”

With Arsenal’s clash against West Ham postponed due to a strike on the London Underground, fifth-placed Everton, who host Wigan, Tottenham, who travel to Villa, and West Bromwich Albion, on their travels at QPR, all have a chance to move into the top four.

Fixtures (1500GMT unless stated):

Aston Villa v Tottenham (1730GMT), Everton v Wigan, Fulham v Southampton, Man Utd v Newcastle, Norwich v Chelsea, QPR v West Brom, Reading v Swansea, Stoke v Liverpool (1945GMT), Sunderland v Man City