Sevilla coach Jose Luis Mendilibar was surprised by Manchester United's lack of fight after their 3-0 victory.
Youssef En-Nesyri struck twice and Loic Bade also scored as Sevilla reached the Europa League semifinals 5-2 on aggregate.
Mendilibar said: "This is a team that's used to greater things.
"We came from an awkward situation in Manchester, where we drew 2-2 without doing things right, and people believed that we could do it. In the end we did it. It's surprising for us to win a game against Manchester United without struggling and with such forcefulness, it's not easy."
On how he's turned Sevilla around, Mendilibar also said: "Simplicity, I imagine. I am the way I am and that's that. I've been in a lot of teams at all levels. I started in regional football and now we're in the semis of the Europa League with a good team. I've not complicated things for anybody. It's simplicity above all, which is a key thing in football."
