Iago Aspas hit the post for Celta with seven minutes left to play before Marco Asensio scored Real Madrid's third goal on the break in the fourth minute of injury time on Saturday, Xinhua news reports.
Hakim Ziyech and Emerson scored one goal each in the match to power the Premier League side into the quarter-finals of the competition. In the first-leg match, Chelsea had registered a 1-0 win over Atletico Madrid.
The result allows FC Barcelona to move to within three points of Atletico and two ahead of Real Madrid thanks to a 2-0 win away to Osasuna on Saturday night
Barca coach Ronald Koeman said in his pre-game press conference that this game and Saturday's trip to Sevilla were vital for his side's title chances, and he made changes to try and keep his squad fresh
What was Atletico's home leg had to be played in Bucharest due to a ban on flights from Britain to Spain to try and stop the spread of coronavirus variants.
The buildup was overshadowed by Serge Gnabry testing positive for the coronavirus on Tuesday after he had taken part in the team's final training session for the game.
Barcelona had its first defeat under Ronald Koeman when it lost 1-0 at Getafe on Saturday, right after Madrid was beaten 1-0 at home by recently promoted Cádiz
Two consecutive scoreless draws quickly dampened the hype surrounding Atlético's new attack after it had opened the season with an impressive 6-1 victory over Granad
