Manchester United have dropped two precious points in a 0-0 draw at 10-man Crystal Palace, giving Premier League leaders Chelsea the chance to go eight points clear if they beat Norwich City later.
Champions Arsenal kept their slim title hopes alive on Saturday after a Thierry Henry hat-trick gave them a 3-0 home victory over Portsmouth, though they remain seven points adrift of the leaders having played two games more.
Chelsea have 68 points from 27 games, with United on 63 from 29 games and Arsenal third on 61, also from 29. Jose Mourinho's team, on course for their first league title in 50 years, kicked off at Carrow Road at 1715 GMT.
Southampton improved their survival hopes with a 1-0 home win over Tottenham Hotspur while Aston Villa and Newcastle also enjoyed morale-boosting victories.
The Champions League offered a potential distraction for Chelsea, United and Arsenal. All three trail before their return legs against Barcelona, AC Milan and Bayern Munich respectively in midweek.
United, who were seeking a seventh straight league win, rested Wayne Rooney, Cristiano Ronaldo and Paul Scholes at the start and were fuming after Roy Keane was denied in the first half by an offside flag.
The visitors' frustration then increased as Palace's Hungarian goalkeeper Gabor Kiraly saved superbly from Ruud van Nistelrooy.
Palace's task was made all the harder when the 64th-minute dismissal of Greek midfielder Vassilis Lakis left them to play the last half-hour with 10 men but they held out thanks to a combination of luck and poor United finishing.
Manchester United striker Ruud van Nistelrooy is confident that his side can overturn their first leg deficit and knock AC Milan out of the Champions League next week.
The Dutch international was restricted to a substitute's cameo in the first leg at Old Trafford last week but seems certain to start at the San Siro on March 8 as United look to overturn the Italian's 1-0 lead.
And although some see United's task as a massive uphill battle, Van Nistelrooy is confident they can progress by beating the Italian giants in the San Siro.
"We go there with a clear task. We have to win. It is not a simple thing to do but we have to go for it and we will go for it," van Nistelrooy said.
"We were all disappointed at what happened in the first game but as time has gone on, we are all starting to look forward to the Milan game. We still believe in ourselves and we are capable of doing it," he added.
United will hope to draw on their previous good results in Italy, including their 3-2 semi-final win over Juventus after falling two goals behind in 1999.
" We want to look forward, not back but that win against Juventus is part of the great history of our club. Knowing there are players in this current squad capable of doing that gives us the confidence to go there and do it," van Nistelrooy.
Manchester United striker Ruud van Nistelrooy is pleading for patience as he battles back to full fitness.
The prolific Holland international earned the praise of Sir Alex Ferguson for his performance in the 2-1 win over Portsmouth on Saturday but, despite playing the pass to set up Wayne Rooney for the winner, still looked off the pace.
It was van Nistelrooy's first league start for three months after a 30-minute appearance against Milan in midweek following his recovery from an Achilles injury.
The 28-year-old admits it will take time to reach the level of fitness that brought him 122 goals in just 161 first-team starts.
But the former PSV Eindhoven striker does not want to be judged too quickly and aims to be fully fit for the Milan return on March 8.
"It was fantastic to start against Portsmouth, it felt like my first game again," he said.
"That is what I worked so hard for but I also have to be patient.
"I have been out for a while and I can feel it. I have been training with the first team squad for a week and a half but I know I am still missing a bit of timing, so now I just need games.
"At least I feel fresh and have got virtually a full game under my belt. Now I build on that performance and move on."
Ferguson has confirmed van Nistelrooy will start next Saturday's Barclays Premiership clash with Crystal Palace when victory will reduce Chelsea's lead at the top to three points.
For virtually the first time since he moved to England, van Nistelrooy has competition in the United scoring stakes with Wayne Rooney's double on Saturday moving him onto 15 for the season, three clear of his fellow forward.
But van Nistelrooy is happy to have competition for places in the United line-up as they continue their quest for silverware this season.
"Wayne is having a great season," van Nistelrooy added.
"For his age, he is a tremendous player and it is great to have someone like that on our side.
"Saturday is a really big game for us. We want to close the gap on Chelsea to three points, but we also want a good result to lift confidence before we go to Milan."
Sir Alex Ferguson hailed Wayne Rooney as "absolutely magnificent" after the teenager kept Manchester United's bid to catch Chelsea at the top of the Premiership on track with a superb double strike against Portsmouth.
A 2-1 win cut Chelsea's advantage back to six points. The London club, who play Liverpool in the League Cup final on Sunday, retain a game in hand.
But by the time they play Norwich next Saturday, United could have reduced their lead to just three points if they beat Crystal Palace earlier in the day.
Ferguson acknowledged his side had been short of their best after a draining Champions League defeat by AC Milan in midweek. But he was unstinting in his praise for Rooney.
"He was by far our best player," the Scot said. "He was absolutely magnificent today. And he's a winner, he was one taking the baton up and making the run for the line. The whole day he was on song."
For most of the second half, after Gary O'Neill had cancelled out Rooney's sweetly taken opener, it looked as if Portsmouth, the last side to beat United in the league back in October, would defy the odds once more.
But Rooney had other ideas. With ten minutes left, the teenager collected a pass from Ruud van Nistelrooy in his stride and surged into the box before finishing with aplomb to make it six league wins in a row for Ferguson's side.
Ferguson revealed that Rio Ferdinand had missed the match with a hamstring injury while skipper Roy Keane was rested and Gary Neville came off injured at half-time.
"All these changes do not help in terms of continuity but the most important thing is that we won the game," he said.
"Over the years I've seen these kind of results result in us going for championships. It also stressed the determination and perseverence of Manchester United."
While United continue to hold out hope that Chelsea will crack, Arsenal's lingering hopes of retaining their Premiership title appeared to have been crushed after a 1-1 draw at relegation-threatened Southampton that left them ten points behind Chelsea.
Van Nistelrooy made a 30-minute appearance against AC Milan in midweek after three months out with an Achilles injury and the Dutchman will now step up his drive for match fitness by taking his place in what is likely to be a much-changed starting line-up.
"Ruud will be in from the start tomorrow, no doubt about that," Ferguson told the Manchester Evening News.
"It is always difficult coming on off the bench, especially after a long time out with injury and in a match like that. But Ruud did really well."
Prior to the FA Cup win over Everton, Ferguson said some of his senior stars would need a rest this weekend, so Roy Keane is almost certain to stand down, while Wayne Rooney might also be granted a break.
Roy Carroll is expected to continue in goal despite his costly blunder against Milan, while Mikael Silvestre and Phil Neville are hoping for a recall.