Forlan had started the game on the bench but he was called into action at the end of the first half when Sergio Aguero was forced off with a facial injury, and the Uruguayan ended up being his side's hero.

He struck in the 90th minute just as the tie looked set to go to extra time with the two sides locked at 1-1 - the same scoreline from the first leg.

Earlier, Kader Keita had quickly cancelled out Simao Sabrosa's 62nd-minute opener for Atletico, before Galatasaray were reduced to 10 men in the 80th minute when Caner Erkin was sent off.

Atletico had looked to have wasted their chance after dominating the first leg at the Vicente Calderon before conceding a late equaliser to Keita, but Quique Sanchez Flores' side recovered from that setback in perfect fashion tonight to set up a last-16 clash with either Everton or Sporting Lisbon.

Despite the blow of losing Aguero towards the end of a goalless first half, Atletico started the second period well and first-leg goalscorer Jose Antonio Reyes went within a whisker of putting his side ahead when he struck the woodwork.

That was in the 51st minute but Atletico only had to 12 more minutes to take the lead through their other winger, Simao.

Antonio Lopez's throw-in was headed on by Jose Manuel Jurado and Simao stole in to fire past former Atletico custodian Leo Franco in the home net.

Atletico's lead lasted just three minutes though before they were undone for the second time in successive matches by Keita.

Galatasaray captain Arda Turin's cross to the far post was perfect for Keita, and his header was too good for Sergio Asenjo.

That was a big blow for the Spanish side, but they received a boost in the 80th minute when Erkin was handed his marching orders after being shown a second yellow card.

Erkin's dismissal gave Atletico the upper hand and they made sure they took full advantage as Forlan fired home from inside the area to put the Primera Division side through to the next phase.