Manchester City lost 1-0 to Arsenal to fall eight points behind Manchester United, who beat QPR earlier on Sunday.
A rasping drive from Mikel Arteta won the game for the Gunners - who leapfrogged north London rivals Tottenham - in the 87th minute after applying incessant pressure on the Citizens' goal.
Mario Balotelli, fortunate not to have been red carded in the first half for a malicious challenge on Alexandre Song, was sent off shortly after Arteta's winner for an unnecessary foul on Bacary Sagna.
United had already beaten QPR in controversial manner in the earlier kick-off. Wayne Rooney dispatched a 15th minute penalty after Shaun Derry was adjudged to have hauled down Ashley Young, who was in fact in an offside position.
Tony Fernandes appreciated United fans' sincerity:
He also appeared to fall theatrically under minimal contact from the former Leeds United midfielder, but referee Lee Mason dismissed Derry for preventing a goalscoring opportunity.
Rafael da Silva missed a great chance to double the lead in the 59th minute as Rs goalkeeper Paddy Kenny tipped his effort on to the woodwork, before man of the match Paul Scholes effectively ended the contest in the 68th minute. Michael Carrick saw a rasping drive smack the post late on too.
For Arsene Wenger's side, a draw would have been enough to see them move up to third after Tottenham's goalless draw at Sunderland yesterday, but were relentless in their desire to beat City.
In what was a thoroughly deserved victory, Robin van Persie saw a header inadvertently cleared on to the crossbar by team-mate Thomas Vermaelen in the first period, and then hit the post in the 62nd minute when expertly found by Song.
Wenger suggested Balotelli should have been substituted:
Joe Hart tipped a Theo Walcott strike on to the post soon after, which Vermaelen inexplicably failed to score with the follow up, as Joleon Lescott then diverted Yossi Benayoun's effort on to the woodwork for a fourth time.
But the Gunners finally breached their hosts when the Spaniard Arteta robbed David Pizarro of possession and fired past Hart from 25 yards.
Gallery of today's Premier League football:
Subdued, City appeared rocked by Yaya Toure's early withdrawal after he picked up a knee injury in a challenge with Song. The 28-year-old was replaced by the Chilean Pizarro, whose mistake led to the winner.
Again Balotelli hogged the headlines for all the wrong reasons. Feasibly he may have played his last game in laser blue should the FA take retrospective action against his challenge on Song, and City manager Roberto Mancini admitted he hoped they would take action against him.
On a day which many have decided the title race is over, it was Arsenal's number eight, who widened the gap to eight points.
Balotelli sees red for the fourth time in his City career