On the night of this match, Ancelotti remarked that he was "saddened" about Chelsea's poor form, but his Real Madrid club only added to Chelsea's difficulties.
Real was far from seamless, but they did enough to build a substantial lead as they aim to win the competition for the 15th time in a row.
Vinicius Junior and Rodrygo were a handful for Real, who had 18 attempts, although Courtois was a solid last line of defence.
Rudiger's final block, which denied Mount, proved crucial. After helping Chelsea win the Champions League in 2021, the German was a sensible option when he joined Real Madrid on a free transfer in June.
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After losing to champs Real Madrid at the Bernabeu, Chelsea must do everything necessary to reach the Champions League semi-finals.
Real Madrid manager Carlo Ancelotti had the perfect start against his former team thanks to Karim Benzema's tap-in, his 90th goal.
Real Madrid's lead was cut short in the 59th minute when Chilwell was sent off for fouling Rodrygo as the Brazilian attacker threatened to score.
Chelsea fought hard, but Real Madrid scored what could be the decisive second goal when substitute Marco Asensio finished well after the visitors were caught off guard by a short corner.
After a lukewarm performance against Wolves in Frank Lampard's first game back as interim manager, Chelsea carried more of an attacking threat and had their own chances.
When the game was still scoreless, Joao Felix pushed Thibaut Courtois into a smart save before the former Chelsea goalie produced a fine diving save to deny Raheem Sterling an equalizer.
