London: Danny Welbeck, making his first appearance of the season as a late substitute, headed a stoppage-time winner as Arsenal boosted their hopes of winning the Premier League title with a 2-1 home win over league leaders Leicester City.
Welbeck, who had not played since last April after a series of injuries, came on after 83 minutes and scored in the fifth minute of stoppage time when he glanced home a Mesut Ozil free kick to secure the victory.
The win lifted Arsenal to 51 points, two behind Leicester, who played most of the second half with 10 men after defender Danny Simpson was sent off in the 54th minute.
Tottenham Hotspur who started the day in second place and Manchester City in fourth meet later on Sunday.
"It was a pivotal moment today because the mathematics meant it could be eight points or it could be two points. That is a great change," Arsenal manager Arsene Wenger told Sky Sports.
"There's a long way to go, we play a lot of big teams. But we had a bad spell where we couldn't win for four games and have now won two on the bounce. We have come out of that bad spell and still have a good chance."
Leicester, seeking a first ever top-flight title, had not beaten Arsenal in their last 18 league matches but after surviving some early pressure, took the lead in the 45th minute when Jamie Vardy scored with a penalty after referee Martin Atkinson ruled that he had been fouled by Nacho Monreal.
Vardy smashed home his 19th league goal of the season giving Petr Cech no chance of saving but the balance of power swung heavily in Arsenal's favour after Simpson's dismissal.
He was booked twice in five minutes, the second time for a clumsy challenge on Olivier Giroud and most of the second half was played out in Leicester's half of the field.
Arsenal's dominance paid off after 70 minutes when substitute Theo Walcott equalised from close range after Giroud's header found him in space.
However they could find no way past goalkeeper Kasper Schmeichel -- who made a series of excellent stops -- until the dying seconds when Welbeck, rose above the defence to seal a hugely significant victory.
Leicester manager Claudio Ranieri told Sky: "We are still top of the table -- we must carry on and smile. We lost to our opponents -- we must say well done."