Van Nistelrooy, starting from the bench again despite netting the winner against West Ham in midweek, converted Louis Saha's cross on 79 minutes to seal a 2-1 win at the Reebok Stadium and breathe new life into the title race.

Saha had cancelled out Kevin Davies's opener for Bolton.

"It's our best result of the season, maybe," United manager Alex Ferguson told Sky Sports after his side inflicted a first home defeat on Bolton in 22 games in all competitions.

"It was (a performance) of determination and grit because the pitch was not very good ... we kept on plugging away until we got the winner."

Chelsea were frustrated by relegation-threatened Birmingham City, the Londoners held at St Andrews in a lunchtime kickoff.

With six games to play, Chelsea have 79 points from 32 games with United on 72. Third-placed Liverpool (67) eased to a 2-0 win at strugglers West Bromwich Albion, Robbie Fowler and Djibril Cisse scoring first-half goals at the Hawthorns.

Thierry Henry scored twice in Arsenal's 5-0 demolition of Aston Villa, who are being dragged into the relegation dogfight, while Tottenham Hotspur had defender Michael Dawson sent off in a 3-1 defeat at Newcastle United.

Spurs remain in the fourth Champions League place on 55 points and bitter rivals Arsenal moved into fifth, two behind after running Villa ragged at Highbury.

At the bottom, Portsmouth's third successive win, 3-1 over Fulham at Craven Cottage, gave the south coast side hope of escaping the drop. Bottom side Sunderland drew 2-2 at Everton.

Van Nistelrooy has endured a frustrating few weeks at Old Trafford, Ferguson preferring Frenchman Saha to play alongside Wayne Rooney.

The Dutchman was again left out of the starting side but gave Ferguson food for thought with a typically clinical finish, his 150th goal for the club.

"We know when he comes on he's going to do it because he's the best finisher in the game," said Ferguson. Van Nistelrooy and Henry lead the league goalscorers' list with 21 each.

Chelsea manager Jose Mourinho was unhappy with another unconvincing display away from home and his side have won just one from their last five on their travels.

"I am concerned, I want to win every game, I'm not happy with the performance and result," he told Sky Sports.

"It's (the title) in our hands. The important thing is we keep winning our matches at home and we will be champions again."