Arsenal thrashed Middlesbrough 7-0 to gain ground in the race for Champions League places on Saturday while fourth-placed Tottenham Hotspur were beaten 1-0 at Liverpool and Manchester United lost 3-1 at Manchester City.
At Highbury, Thierry Henry scored a hat-trick and there were also goals for Philippe Senderos, Robert Pires, Gilberto Silva and Alexander Hleb. Liverpool's victory came courtesy of Harry Kewell's first goal for more than a year.
Arsenal remain fifth, on 37 points from 21 games. Spurs are fourth with 40 from 22, Liverpool have 44 from 20 with United on 45 from 22.
Chelsea, 13 points clear at the top on 58, visit bottom club Sunderland on Sunday.
Elsewhere on Saturday, Everton won 1-0 at Portsmouth, West Ham United triumphed 2-1 at Aston Villa, Charlton Athletic beat Birmingham City 2-0 and Fulham defeated Newcastle United 1-0. Blackburn Rovers were held 0-0 at home by 10-man Bolton Wanderers, who had Japan midfielder Hidetoshi Nakata sent off.
The day began with an upset in the 145th Manchester derby as United completed a painful week.
Goals by Trevor Sinclair and Darius Vassell in an eight-minute spell late in the first half put City in control.
United briefly made it 2-1 with a 76th-minute Ruud van Nistelrooy goal but, down to 10 men after a 66th-minute red card for Cristiano Ronaldo, they were generally toothless in attack and City ended the day in style with a sweet strike by substitute Robbie Fowler.
United's third league defeat of the season followed their goalless FA Cup draw with minor league Burton Albion last Sunday and a 1-1 draw at Blackburn Rovers in the first leg of their League Cup semi-final in midweek.
"We didn't play well enough in the first half, we gave the ball away too much and our last-third play wasn't good enough," manager Alex Ferguson told United's in-house television station MUTV.
BLUE SMILES
As ever though, red frowns equalled blue smiles.
"My team picked up one point out of 12 over Christmas and were a bit low on confidence maybe but we deserved it," City manager Stuart Pearce told Sky Sports.
"We looked like the team who were up for a derby match and took our chances when they came."
United's defeat allowed Liverpool to gain ground as they edged Tottenham in a heavyweight encounter at Anfield.
The game was short on chances and settled by a superb volley from Australian midfielder Kewell after an hour.
Tottenham, who had defender Paul Stalteri sent off three minutes from time, could have lost by more but for a good display by goalkeeper Paul Robinson.
Arsenal totally outclassed a Middlesbrough team being sucked towards the relegation zone as the Londoners matched their 7-0 demolition of Everton last May.
Playing classic, high-speed football they were 4-0 up at halftime and Henry's third, after 68 minutes, took him level with 1930s winger Cliff Bastin as the club's leading league scorer with 150 goals.
"We struck hard and early in the game and for the young defence of Middlesbrough that can be disheartening," said Arsenal manager Arsene Wenger.
Wenger also felt Henry's decision last week to commit his future to Highbury had contributed to the performance.
"Uncertainty has been a weight on the team and it gave the team and him a lift to clear the air," he said.
Injury-hit Middlesbrough, without a league win since November, had Brazilian Doriva sent off for a second booking 18 minutes from time.
"You can't come to places like this with six teenagers on the park, and with Thierry Henry in the form he is in they can rip any side apart," said Boro manager Steve McClaren.
"This is a big lesson for them. At the moment it hurts but we are determined to bounce back and once everybody is back and fit we have the quality to get out of the situation we are in."
