Manchester City were held to a 2-2 Premier League draw by Arsenal in Manuel Pellegrini's final home game, keeping Manchester United's hopes of Champions League football alive.
United cut the gap to City to one point by beating Norwich City 1-0 on Saturday and can now go a point clear of their neighbours with victory over West Ham on Tuesday following Sunday's entertaining game at the Etihad Stadium.
Sergio Aguero opened the scoring, netting for the sixth straight league game in the eighth minute, but Olivier Giroud's first goal in 16 Premier League appearances restored parity two minutes later.
The visitors were forced to withdraw Danny Welbeck shortly after with an injury that will likely give England manager Roy Hodgson cause for concern and City appeared poised to leapfrog Arsenal into third place and all but end United's top-four hopes when Kevin De Bruyne fired in from the edge of the area in the 51st minute.
However, Alexis Sanchez opened the door for United by converting at the end of a wonderful one-two with Giroud to score his sixth goal in his last seven league matches and put the Gunners five points clear of Louis van Gaal's men.
City could not find a way through the Arsenal defence for a third time and now face a nervous wait to see what United do in the final game at Upton Park ahead of their last-day trip to Swansea City.
Aguero broke the deadlock after City had spent the opening exchanges camped in Arsenal territory, delivering another demonstration of his finishing prowess with a fine strike from just inside the area.
The Argentina international met Fernandinho's clever knock down with a fierce shot past Petr Cech and into the bottom-right corner.
But Giroud responded almost instantly, taking advantage of some poor City marking to power Mohamed Elneny's corner beyond Joe Hart and break his duck after former Arsenal defender Gael Clichy had conceded the set-piece by heading a cross narrowly wide of his own goal.
Arsenal's cause was dealt a blow in the 21st minute as Welbeck limped down the tunnel, the striker appearing to injure his right knee during a battle for the ball with Bacary Sagna.
City had the better of the closing stages of the first half but struggled to created chances, however, six minutes after the restart De Bruyne restored the hosts' advantage with a fine solo effort, bursting in from the left and letting fly from the edge of the area.
Theo Walcott failed to find the finish to beat the onrushing Hart at the other end but Sanchez atoned for his team-mate's miss in superb fashion in the 68th minute.
The Chile forward linked up brilliantly with Giroud, who played Sanchez in to emphatically level matters with a confident finish.
De Bruyne then tested Cech with a curling free-kick before playing in Aguero with an exquisite chipped pass, only for the striker to send his half-volley wide of the left-hand post.
Arsenal held on despite Wilfried Bony striking the crossbar late on, meaning City's prospects of returning to the Champions League are now out of their hands.
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