Olivier Giroud's spectacular overhead kick gave Thomas Tuchel's men victory in Bucharest.
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Chelsea will take a 1-0 lead back to London in this round of 16 tie thanks to Olivier Giroud's sensational overhead kick in Bucharest.
Match in brief
Chances were hard to come by in the opening 45 minutes with Thomas Lemar and Timo Werner both failing to turn in teasing crosses at either end. The German striker did at least manage to sting the palms of Jan Oblak with a rising drive as Chelsea had the better of the first half.
The pattern of the game continued after the interval until Mario Hermoso's attempted intervention popped the ball up for Giroud to acrobatically dispatch past the scrambling Oblak and end Chelsea's ten-game winless run in the UEFA Champions League knockout stages.
Player of the Match: Olivier Giroud (Chelsea)
"For the build-up to the goal and then his execution, it must go to Giroud. A great goal which made the difference. For the goal, he also won the ball on the halfway line and controlled it into the path of the supporting player."
Packie Bonner, UEFA Technical Observer
Joe Walker, Atlético reporter
It's not often you say Diego Simeone got it wrong and, to be fair, if it wasn't for a goal of the season contender he might have had it spot on. However, as it is, a defensive display was undone by a piece of magic and a first-ever knockout round defeat at home for the Argentinian means Atleti have it all to do in the return leg.
Jon Phipps, Chelsea reporter
A dominant performance from Chelsea and thanks to a moment of inspiration from Giroud, they are in pole position. The hosts allowed them to have lots of the ball and, although their final pass was lacking most of the time, eventually they got the goal. At the other end they were largely untroubled by an Atlético side who lacked a spark. The only downside was losing Mason Mount and Jorginho to suspension but, aside from that, a fine European bow for Thomas Tuchel.
Olivier Giroud, Chelsea striker: "We came here with strong intentions to win, play our game, and we knew how we could give them trouble offensively. We have been strong at the back, in [our] defensive shape, and we're very pleased with the win. It was a deserved win. I did not know what to think about the goal, I just focused on hitting the overhead kick and was pleased to see it go in. Good for the team, good for me."
Koke, Atlético captain: "We'll go over to London with the idea of winning the game. We'll bounce back from this. It's been a tough week but we need to carry on fighting and competing. We know we need to go to London and win. If we score twice, we go through."
Thomas Tuchel, Chelsea manager: "We knew they were ready to suffer with eight people in the box. The intention was to keep the intensity high. This is what we did very well. We never let them breathe or come out for counterattacks. We have a big reward with this result. This is one of the toughest challenges, to open a defence like Atlético."
Diego Simeone, Atlético coach: "Both sides worked really hard. There were really few opportunities to score and they took theirs, but apart from that it was really even. We were solid defensively, we were good in transition, we had the odd chance. The second half was very even, neither keeper really made a save."
• Atlético had just one shot in the first half, their lowest total after 45 minutes in a UEFA Champions League match since the 2016/17 semi-final first leg against Real Madrid.
• Giroud last scored in the UEFA Champions League knockout stage on 17 March 2015, in Arsenal's 2-0 away win in the second leg of their round of 16 tie against Monaco.
• Giroud has scored a personal-best six goals in this season's competition. He becomes the first Chelsea player to hit that tally in a UEFA Champions League campaign since Didier Drogba in 2011/12.
• Chelsea have never been eliminated from UEFA competition after recording a first-leg away victory, winning 12 ties out of 12.
• Atlético have lost all seven UEFA competition ties in which they were beaten in the home first leg.
Atlético: Oblak; Llorente, Savić, Felipe, Hermoso (Vitolo 84); Correa (Dembélé 82), Saúl Ñíguez (Torreira 82), Koke, Lemar; João Félix (Renan Lodi 82), Luis Suárez
Chelsea: Mendy; Azpilicueta, Christensen, Rüdiger, Alonso; Mount (Kanté 74), Jorginho, Kovačić (Ziyech 74); Hudson-Odoi (James 80), Giroud (Havertz 87), Werner (Pulišić 87)
Both teams have a number of domestic fixtures prior to the second leg in the English capital on Wednesday 17 March.
28/2: Villarreal (a)
7/3: Real Madrid (h)
10/3: Athletic Club (h)
13/3: Getafe (a)
28/2: Man. United (h)
4/3: Liverpool (a)
8/3: Everton (h)
13/3: Leeds United (a)
*League fixtures unless otherwise stated