I think this season Sevilla was very lucky to defeat Manchester United . Manchester United have done well in their performance this season, Sevilla was just lucky that the time they met with Manchester united , Manchester United was in their worst state , some players were on injuries and other mistakes that led to the defeat of Manchester United.
But I think it's not just luck, because Manchester United also difficulty in previously a few seasons to win against Sevilla. Look at the head to head history of this both teams if Sevilla are lucky, so they don't have a good record with four wins in the last seven meetings against Manchester United including this match.
Next Sevilla will against Juventus in semifinals, after beating Mancheter United very well, maybe they will qualify for the finals too. But Juventus which also won against Sporting before, making them even more confident to win against Sevilla later.
MU is performing badly, and Sevilla is starting to show a better game. no luck. what was fortunate was that the two met and Sevilla took advantage of that with their hard work.
Sevilla did have problems at the start of the season but they fixed everything even though in the League they were late to get up. but MU like failed to do well. they have too many problems this season. not a good start, even in the middle of the season they had improved but in the end they were not consistent. many fans are not satisfied with MU.