Olivier Giroud's magnificent bike kick broke Atletico Madrid's level of resistance and earned Chelsea a crucial away target on Tuesday, a 1-0 victory supplying Thomas Tuchel's side a slender gain in the Champions Group last 16.
Giroud's acrobatic hit was initially eliminated for offside but stood after VAR showed Mario Hermoso had got the final touch, delivering an enormous blow to Atletico's expectations of achieving the quarter-finals.
"I didn't know very well what to think about the target, I just centered on striking the ball," said Giroud. "I take pleasure in an overhead kick and I was just pleased to see the ball strike the back of the web. I had no clue about getting offside or certainly not."
Diego Simeone's area had put on a typically disciplined defensive performance until that time but Giroud's point in time of genius means they have to score in London on March 17 if they are to prevent an early exit.
It also continues a worrying dip for Atletico, whose lead in La Liga can be under threat after a single win in four suits.
"If you'd thought to me found in September we'd lose this first leg 1-0 and be top of the league, I'd possess signed for that for certain," said Simeone.
"The results aren't going for us so we need to work, work, do the job and work."
Chelsea, meanwhile, approved their biggest check since Tuchel was appointed towards the end of January, backing up a solid run against lesser lamps in the Premier Group with a polished screen against among Europe's elite.
"We knew their strengths and handled them," said Giroud. "We have to stay focused nowadays and finish the work."
Giroud's goal in the 68th minute was only the third Atletico have conceded found in 14 home hip and legs of the Champions League knockout stages under Simeone, whether or not this fixture was in the home only in name.
Constraints imposed by the Spanish authorities meant the game had to be played in Bucharest rather than Madrid, despite the return match remaining in Stamford Bridge in 3 weeks' time.
Tuchel admitted the switch gave his area an edge but Simeone refused to complain on Monday, insisting he felt fortunate to take up through the pandemic, "however and wherever that could be".
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Their defeat makes it three home losses away of 3 for Spain's teams on the Champions League previous 16 up to now, after Barcelona were thrashed by Paris Saint-Germain and Sevilla were beaten by Borussia Dortmund last week.
Callum Hudson-Odoi started for Chelsea, despite Tuchel criticising the 20-year-old's frame of mind against Southampton on Saturday.
Atletico started with Suarez, Joao Felix and Angel Correa but an attacking line-up used a typically defensive form, a six-man wall quickly forming in front of Chelsea in the beginning stages.
The first half was tight, each side able and then create openings but failing to obtain the pass to produce a chance.
Edouard Mendy's heavy contact in the opening mins practically gave the chasing Saul Niguez a good tap-in while Timo Werner's angled shot was first saved by Jan Oblak and Suarez miskicked in the near post.
Chelsea looked most dangerous straight down the flanks, where Marcos Alonso and Hudson-Odoi pushed Atletico backside. Atletico possessed space on the break but lacked the accuracy to capitalise.
Felix sprung into lifestyle early in the next half, feeding Thomas Lemar and conference the Frenchman's cross with an acrobatic volley that flew more than.
The overall game looked destined to complete goalless limited to Atletico to briefly lose shape, allowing the instinctive Giroud to take advantage.
Alonso had raced from Marcos Llorente straight down the left and his cross was diverted backwards to Giroud, who brilliantly bicycle-kicked in to the corner, but looked offside, limited to the replay showing it had been Atletico's Hermoso who had given him the assist.
The target stood and Chelsea's players celebrated, seemingly as stunned as anyone and delighted with a treasured advantage.