In December 2021, the Champions League round of 16 draw was declared void due to a technical error, forcing UEFA to redo the entire process. The mistake, attributed to a software issue with an external service provider, led to incorrect team eligibility being displayed during the draw.
Manchester United were wrongly listed as potential opponents for Villarreal, despite having been in the same group, and were omitted from the list of possible opponents for Atletico Madrid. The error was flagged by Atletico Madrid, who issued a statement calling for an explanation and resolution.
UEFA confirmed the draw was void and would be redone at 3 p.m. CET. In the re-run, three of the four English teams received different opponents. Chelsea were the only side to face the same opponent, Lille, in both draws. Liverpool initially drew Red Bull Salzburg but later got Inter Milan, while Manchester City's opponents changed from Villarreal to Sporting CP.
Manchester United were ultimately paired with Atletico Madrid, as they had been in the original draw. United drew 1-1 in the first leg in Spain but lost 1-0 at home to exit the competition. Atletico's run ended in the next round against Manchester City, losing 1-0 on aggregate.
