Michy Batshuayi snatched a stunning 2-1 win for Chelsea with the last kick of the game at Atletico Madrid as Diego Costa looked on from the Wanda Metropolitano stands.
Antonio Conte's Premier League champion was unfortunate to be behind when Antoine Griezmann scored Atleti's first European goal at its new home from the penalty spot.
The opener from the man Costa will join in a dream forward line from January onwards, having finalised his Atletico return from Chelsea on Tuesday, arrived five minutes before half-time but Alvaro Morata gave another indication that Conte's side will cope perfectly well without its old talisman.
Morata nodded in a 59th-minute cross from the exceptional Eden Hazard to move on to seven goals in all competitions this season and worse was to follow for Diego Simeone's men.
Instead of launching a free-kick into the area as the allotted period of injury time expired, Chelsea calmly worked possession around, with Marcos Alonso picking out substitute Batshuayi for a simple finish that left the watching Costa ashen faced.
Chelsea is top of the standings after back-to-back wins, two points clear of Roma, while Atleti has ground to make up in its pending double-header against Qarabag.
Conte handed a start to the fit-again Hazard and Chelsea's influential playmaker began brightly.
Hazard embarked upon a driving run in the fifth minute, sliding through a pass for Morata to drag wide, before cleverly cutting in from the left to fire into the side netting.
Morata was off target once more from a similar position to the right of goal inside the Atletico penalty area, provoking an animated response from Conte on the touchline.
Chelsea's 3-5-2 was causing Atleti persistent problems and the jewel in the formation, Hazard, engineered space 25 yards out in the 13th minute to unleash a vicious swerving drive against the post, with home goalkeeper Jan Oblak rooted to the spot.
Oblak was a necessarily more active participant after the first half ticked past midway and Morata's header from David Luiz's raking pass forced him to tip over.
Atletico belatedly steadied itself and took the lead having been on the back foot.
Luiz needlessly grabbed Lucas Hernandez's shirt as the defender looked to attack a near-post corner and Griezmann outfoxed Thibaut Courtois by sending his spot kick down the middle.
It was almost 2-0 on the stroke of half-time when Courtois parried Koke's low drive dangerously into the path of Saul Niguez, who sidefooted narrowly wide.
Saul got above Tiemoue Bakayoko to head past the post from a Koke set-piece early in the second half, while a wicked cross from Cesar Azpilicueta flashed agonisingly between Morata and the face of goal at the other end.
It was no surprise when Hazard served as the architect of the away side's equaliser, curling in a sumptuous ball from the left and obliging Morata to nod home.
Uncharacteristic panic suddenly gripped the Atleti defence and after a clutch of red-and-white shirts scurried towards Hazard in vain, an unmarked but stumbling Cesc Fabregas was unable to turn in the cutback from close range.
Morata's outing should really have proved more profitable than it was.
The Spain striker streaked away from Lucas in the 75th minute only to misjudge a tame finish, but Batshuayi — on for Morata — clinched the points with a close-range finish deep in injury time.