Jose Gimenez's stoppage-time winner earned Atletico Madrid a 2-1 victory over Inter Milan in the Champions League on Wednesday, inflicting the Italians' first defeat in the competition.
Julian Alvarez opened the scoring for Atletico early on as Diego Simeone's side boosted their chances of a top eight finish following a mixed start to the league phase.
Piotr Zielinski levelled in the second half for Inter but the visitors faded in the final stages and Atletico capitalised.
Gimenez headed home Antoine Griezmann's corner to claim a potentially vital triumph for the Rojiblancos at a rocking Metropolitano stadium.
New Inter coach Cristian Chivu started with Lautaro Martinez and Ange-Yoan Bonny up front, benching Marcus Thuram after Sunday's disappointing derby defeat by AC Milan.
The Italians were also without Denzel Dumfries and Henrikh Mkhitaryan, as they sought to maintain what had been a 100 per cent start to the competition.
The trip to Madrid offered last season's beaten finalists their first true test in Europe this term following four comparatively easy fixtures.
Federico Dimarco twice came close in the opening stages, with Atletico goalkeeper Juan Musso tipping away his free-kick before the Italian wing-back fired narrowly wide when well placed.
Despite Inter's enterprising start it was Atletico who took the lead, with Alvarez drilling home from close range when the ball deflected nicely for him.
Although the strike was initially ruled out for handball against Alex Baena, the referee allowed the goal after a VAR review as it appeared to have hit him in the stomach.
It was Alvarez's 10th goal of the season across all competitions, with the former Manchester City player vital for the Rojiblancos.
Musso, standing in for the injured Jan Oblak, beat away Hakan Calhanoglu's shot from distance as Inter pushed for an equaliser.
The visitors pushed Atletico back for large swathes of the first half and Dimarco came close again with a curling effort which just flew wide of the top corner.
After losses against Serie A rivals Milan and Napoli, inexperienced coach Chivu was hoping to claim his first victory in a big match at Inter's helm.
The Italians almost equalised at the start of the second half as Nicolo Barella brought down a long ball brilliantly and then lofted the ball against the crossbar.
It was no surprise when Inter levelled after 54 minutes, with Bonny teeing up Zielinski to sweep home.
Atletico found some balance after conceding and the pace slowed, with Inter seemingly content to add a point to their tally.
Alexander Sorloth lashed over the bar and Yann Sommer thwarted Griezmann at his near post, as Simeone's side probed for a winner.
Swiss stopper Sommer saved from Marc Pubill as well, with the hosts in the ascendancy in the final stages, and they eventually got their second in the third minute of stoppage time.
Gimenez got his head on Griezmann's corner and the ball flew past Sommer to spark big celebrations and help Atletico rise to 12th, with Inter 4th.