Simeone's side travel to San Mames on Wednesday evening holding a 1-0 lead from the first leg, but Bilbao are unbeaten on their own patch this season.
"They will be looking to start the game with a lot of intensity and then we'll have to respond, because they will be more confident," Simeone told reporters at a press conference.
"The game will be evenly matched and tight. We don't have a formula, as such, for the game; we have a certain playing philosophy and we're not going to change it."
Atletico are the current holders of the Copa del Rey, having beaten Real Madrid in the final last season.