Manchester United overcame a first-half scare to keep their Barclays Premiership title challenge on course with a 4-1 win over Blackburn at Old Trafford on Saturday.

The Red Devils fell behind when Morten Gamst Pedersen's low cross from the left caused confusion in the 29th minute. It took a fine save from Edwin van der Sar and the base of the post to prevent a Michael Carrick own goal, but England Under-21 striker Matt Derbyshire followed up to score.

United drew level after an hour's play when Paul Scholes evaded the challenge of two Blackburn defenders and drilled a low shot past Brad Friedel.

And they forged ahead in the 73rd minute when Cristiano Ronaldo cut the ball back into the path of Carrick who passed it low into the net.

Park Ji-Sung made the result safe by scoring on the rebound after Friedel could only parry a Ronaldo free-kick before Ole Gunnar Solskjaer, back in the fold after injury, added a late fourth.

There was more bad news on the injury front for Treble-chasing United, though, with Nemanja Vidic stretchered off with a dislocated shoulder. He's expected to be out for between four and five weeks.

United remain six points clear at the top after Chelsea stayed in touch with an injury-time winner at bottom club Watford.

The Blues were in danger of falling eight points behind United with the Vicarage Road clash still goalless as it ticked into stoppage time.

But then Salomon Kalou headed home an Andriy Shevchenko cross to break the Hornets' hearts.

Earlier in the day Liverpool leapfrogged Arsenal into third place with a 4-1 win over the Gunners in the lunchtime kick-off at Anfield.

Peter Crouch, who missed England's Euro 2008 qualifying double-header after undergoing surgery for a broken nose, returned to action for the Reds and put them 2-0 up before half-time with a smart near-post finish and a towering header from a Fabio Aurelio cross.

Daniel Agger added a third on the hour before William Gallas nudged in a consolation for Arsene Wenger's team. Crouch completed his hat-trick after 80 minutes with some superb close control to elude Kolo Toure before a smart finish.

In the race for survival, second-bottom West Ham beat Middlesbrough 2-0 thanks to an early Bobby Zamora goal and one on 45 minutes from Carlos Tevez.

The first came when the Argentinian crossed from the right and after two deflections the ball fell to Zamora and he drove in a shot from six yards.

Tevez grabbed the second when Boro made a hash of dealing with George McCartney's cross and he was on hand to fire home.

Unfortunately for Hammers boss Alan Curbishley his old club Charlton also won, cutting the gap between themselves and Sheffield United in 17th to one point with a 1-0 victory over Wigan at The Valley.

Darren Bent kept his nerve to score an 86th-minute penalty, with the result also taking the Addicks within three points of Wigan.

Sheffield United lost 1-0 at Bolton, Kevin Davies making the breakthrough for Wanderers from a Nicolas Anelka assist after concerted pressure to end a run of three consecutive defeats for the UEFA Cup challengers Bolton.

Portsmouth and Fulham drew 1-1 at Craven Cottage, Niko Kranjcar's curling right-foot shot flying into the top corner in the fourth minute with the aid of a slight deflection off Liam Rosenior to give Pompey the early advantage.

But the Londoners snatched a point with a late Ian Pearce equaliser which deceived David James with the aid of a huge deflection.

Manchester City, boosted by their win at Middlesbrough last time out, were victorious again as Emile Mpenza scored the only goal at Newcastle in the 81st minute after Scott Parker had a first-half goal disallowed for the hosts.