Real Madrid struggled to break down 10-man Atalanta before Ferland Mendy scored an 86th-minute winner for a 1-0 win in the first leg of the round of 16.
Madrid entered the game as the big favourites despite a host of injuries, and Atalanta’s chances diminished further when midfielder Remo Freuler was sent off in the 17th minute after being adjudged to have denied a goalscoring opportunity.
But Madrid, who were missing Karim Benzema, Eden Hazard and captain Sergio Ramos, still found it difficult to test Atalanta goalkeeper Pierluigi Gollini until the end of the first half, when he pulled off a great reaction save to keep out Casemiro’s header from a Toni Kroos’ free-kick.
Just as it looked as if Atalanta would hold on for a draw, Mendy received the ball outside the area after a corner and curled a shot into the right side of the net from 20 yards.
The second leg will be on March 16 in Madrid.
The match was played in an empty stadium because of coronavirus restrictions but approximately 5,000 fans were waiting outside the stadium in Bergamo before the game, despite the local health authority urging supporters to stay away. They set off fireworks and flares as they welcomed the team bus.
Atalanta’s chances of beating its more illustrious opponent diminished when Freuler was sent off for barging over Mendy on the edge of his own penalty area.
Atalanta coach Gian Piero Gasperini immediately told midfielder Mario Paalic to start warming up and a decision on who to take off was made for him on the half hour, with forward Duvn Zapata limping after an earlier challenge.
Despite the numerical advantage, Madrid struggled to create goalscoring opportunities until the closing stages of the half when they had a couple of shots deflected off target and Gollini denied Casemiro.
Atalanta forward Luis Muriel almost gave Atalanta the lead instead but fired wide of the left upright. It was left to Mendy to curl home his first Champions League goal.