United and Sevilla meet in Cologne on Monday (AEST) for the right to play against either Inter Milan of Shakhtar Donetsk in the final.

Sevilla comes into the match on the back of a 19-game unbeaten run, boosted by wins over Roma and Wolverhampton Wanderers in its past two outings, while United has lost just once since January.

While United was underwhelming in a 1-0 quarter-final win over Copenhagen, requiring extra-time to emerge victorious, Lopetegui clearly rates Ole Gunnar Solskjaer's men highly.

Sevilla stunned United in the Round of 16 of the UEFA Champions League when they last met two years ago, but Lopetegui is certain the Red Devils are much better now.

"This United is the best Manchester United in recent years, a team that has found its way, that's why they haven't lost in the Premier League since January," he said.

"They have found the space for the many quality footballers that they have. They are complete, they will force us to play a great game to compete with them.

"This is what I hope for tomorrow, a semi-final in a game of maximum difficulty and that will require us at all levels to play collectively.

"We like to play beautiful and important matches. For that we have fought and worked all year. It is an important game against a great opponent.

"We will be able to arrive prepared. We will try to overcome them, no matter how big a team they are."

Sevilla is chasing its sixth title in Europe's secondary competition, having won the UEFA Europa League three times and its predecessor, the UEFA Cup, twice.