Atletico travel to the Camp Nou for the first leg on Tuesday, with Luis under no illusions as to the difficulty of the task.
"Both teams are doing very well. Our playing styles are completely different. We play to defend and counterattack. They play with the ball, to have the possession and tire the rival," Inside Spanish Football quotes the left-back as saying.
"We know each other well, we've played a couple of matched this season. Now we face three more until the end of season. It's going to be a hard match, very hard because we're going to run a lot.
"We're going to have to be physically well, like we've been until now. Barcelona demands your best level, it's clear we have to be very focused. It's a match where they are favourites, but illusion weighs more in this stage of the competition."
The second leg will take place one week later at the Calderon.