Manchester City lost more ground in the Premier League title race after being held to a 2-2 draw by West Ham.
Enner Valencia opened the scoring for West Ham after just 53 seconds, with the striker lashing home from Cheikhou Kouyate’s cross after a powerful run from the midfielder.
Manchester City responded within eight minutes, with Aguero winning a penalty after a foul from Carl Jenkinson, with the Argentinean converting from the penalty spot.
Valencia then made it 2-1 just before the hour mark, capitalising on lackadaisical defending to latch onto Michail Antonio’s quick throw-in and prod past Joe Hart.
But Aguero had the final say, finishing from close range after West Ham failed to deal with Kelechi Iheanacho’s run.
City rise to second in the Premier League, three points behind leaders Leicester and above Arsenal on goal difference. The Gunners face Chelsea on Sunday. West Ham stay sixth.
City’s defence has come under scrutiny this season and it failed its first test at Upton Park as West Ham scored with their opening attack.
Kouyate strode past a non-existent challenge from Yaya Toure and into the area before cutting the ball back for Valencia to slam under Hart.
City almost hit straight back when Aguero got round the back of James Collins, his clever lob beating Hammers keeper Adrian only to come back off the inside of the far post.
But moments later Agureo did haul the visitors level after he had been tripped in the area by Jenkinson, coolly sending Adrian the wrong way from the penalty spot.
Right-back Jenkinson’s evening came to an end moments later when he limped off injured, meaning a quicker-than-expected debut for new signing Sam Byram just three days after completing his switch from Leeds.
Yet despite having been gifted a route back into the game, City’s galaxy of stars were still being outshone by West Ham’s Dimitri Payet.
One clever reverse pass from the French playmaker sent Antonio racing through, and Martin Demichelis earned himself a yellow card for halting the winger’s dart towards goal.
Payet stepped up to take the free-kick and his powerful, curling effort was destined for the top corner until Hart dived full-length to his left to pull off a world-class save.
After the break another sublime touch from Payet sent Mark Noble scampering to the byline before standing up a tempting cross to the far post which Antonio headed narrowly wide.
City were inches from taking the lead, against the run of play, in the 55th minute when Fabian Delph’s low shot hit the foot of Adrian’s post – and moments later West Ham went back in front.
Antonio’s quickly-taken throw-in, of all things, caught the City defence napping and Valencia brushed off Nicolas Otamendi’s feeble challenge before prodding the ball past Hart.
However, with 10 minutes remaining and West Ham defending deeper and deeper, City substitute Iheanacho ran unchecked into the area. His shot rebounded into the path of Aguero who was able to steer the ball past Adrian.
Even then West Ham could have stolen the victory but Kouyate’s stoppage-time header from Noble’s free-kick clipped the crossbar, and City escaped with an unconvincing point.