Diego Simeone conceded on Monday that Manchester City have "better" players than Atletico Madrid but said Chelsea's Champions League success last year shows his team can still reach the semi-finals.
Atletico are the underdogs heading into the first leg in Manchester on Tuesday but Simeone's side have history for upsetting the odds, not least when they defeated Pep Guardiola's Bayern Munich in 2016.
"I have no doubt Manchester city have extraordinary players," Simeone said in a press conference. "They have better players than us, but there are two games to play.
"Manchester City and Bayern are the favourites because of the players have but last season, Chelsea won. They got better, they played as a team and they won, which nobody expected."
Guardiola had earlier refused to be drawn into a "stupid" debate on tactics, amid suggestions the match would be a clash of styles between the possession-based football he favours and Atletico's cruder style under Simeone.
"I'm not going to talk one second about this stupid debate," he said. "Everyone tries to win the game.
"If they win they are right, if we win we are right. It's for the players, the difference will be there."
Manchester United were undone by Atletico's spoiling tactics in the previous round but Guardiola had no time for the notion the Spanish club were an "ugly" team.
"I'm not going to judge what they do, I'll analyse what to do to get a good result to go to Madrid next week," he said.
"What is playing ugly? My team won in Old Trafford 1-0 and Bernardo Silva spent five minutes in the corner. That is not ugly, it's defending the position.
"I never judge the opponents, what they do."
Simeone said three times that he "likes watching Manchester City play" but pointed to City's work ethic under Guardiola as the key to their success.
"What impresses me is how Raheem Sterling, (Kevin) De Bruyne, they run, they pressure, they never think a ball is lost," Simeone said. "This work ethic is what every manager wants."
Meanwhile, Guardiola said he always overthinks his tactics in the Champions league and joked he could even line up with 12 players.
"In the Champions League always I overthink. New tactics, tomorrow (Tuesday) you will see a new one," said the former Bayern Munich coach.
"I overthink a lot, that's why I have very good results in the Champions League. It would be boring if I always played the same way."
Guardiola, who twice won the Champions League as coach of Barcelona, appeared to make fun of his approach by adding: "The movements are different, the players are all different with different personalities.
"That's why I overthink and create stupid tactics. Tonight I will take an inspiration and I'm going to do incredible tactics tomorrow. We will play with 12 tomorrow!"
The reigning Premier League champions have yet to win European football's most prestigious trophy. They came close last year, losing 1-0 in the final to English rivals Chelsea.
City midfielder Bernardo Silva added: "We know it will be very tight. It won't be an open game because that isn't Atletico's quality."