Atleti earned a 1-1 draw from the first leg at Camp Nou, Diego's spectacular long-range strike cancelled out by Neymar's effort 19 minutes from time.
A goalless draw or a win for Simeone's men in the Vicente Calderon next week - where they have lost just once this term - would be enough to see them progress to the last four, but the Argentinian is reluctant to name his side as favourites.
"It will be a very hard and exciting match," he said.
"If we say it's us (as favourites), we'll be arrogant. If we say it's halfway or for them, we'll be the victims.
"We'll compete because the matches against them have been very good."
Atleti lost talismanic striker Diego Costa to a hamstring injury during Tuesday's game, with scans set to reveal the extent of the problem later this week.
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