Lopetegui hailed United as "the biggest team in the world", but said the showdown held no fears for his Sevilla side.
"We are going to play against Manchester United in the next match - they're the biggest team in the world but we're going to be prepared for them," Lopetegui told reporters.
"We're focused on the next game, against a top, historic side, one of the best in the history of the sport who are in great form.
"We will give our best as we always do. To play against them will be really tough, but we'll go into it believing we can beat them."