Liverpool boss Jurgen Klopp is not a fan of Atletico Madrid's style of play but says he has nothing but admiration for "results machine" Diego Simeone.
Klopp questioned Atleti's defensive tactics after the Spanish side knocked Liverpool out of the Champions League at the last-16 stage in the 2019-20 season.
Speaking after his side's 3-2 defeat, seeing them crash out 4-2 on aggregate, Klopp said he "does not understand with the quality they have why they play this type of football".
The two teams face off at Wanda Metropolitano on Tuesday and again at Anfield two weeks later in a couple of crucial games in Group B.
Liverpool have taken six points from six so far, leaving them two points above second-place Atletico after the LaLiga champions followed up a stalemate against Porto with a late win at Milan.
Klopp praised opposite number Simeone ahead of Liverpool's trip to the Spanish capital, the Argentinian having won eight trophies during his decade in charge of Atletico, while also reaching two Champions League finals.
"I was angry and disappointed about a lot of things when I said what I said after the last game," Klopp said at Monday's pre-match news conference.
"We played against a team full of world-class players and they defended with all they have. That's probably the reason I said those things.
"I couldn't respect more what they do. Do I like it? Not a lot, but that's me. I like a different style of football. But it just has to be successful and Atletico have been that, for sure.
"Simeone is the current Spanish champion. He's been there for a long time and has been very successful.
"They play a different system now but they are still the results machine they were before. How Simeone keeps them on their toes with the fight they show I don't know.
"They did well with their signings and have a proper team that looks like possible champions again this year in LaLiga. That's incredible.
"So yeah, what I said before was definitely influenced by my mood on that specific day."
Liverpool beat Watford 5-0 at the weekend to remain second in the Premier League, one point behind leaders Chelsea.
The Reds have scored at least three times in all eight away matches this season, a run that includes a 5-1 win at Porto in their most recent European outing.
Klopp's side have 33 goals to their name this term in all competitions – only Bayern Munich (52) have more among teams from Europe's top five leagues – but the German coach is not expecting a high-scoring affair against Atletico.
"We don't think about the amount of goals we've scored," he said. "We never make the difference between home and away games, though we do enjoy home games more.
"Scoring three goals again, with Atletico next, doesn't sound too likely.
"We know if we win both games against them it's very likely we will go through the group.
"The last time we played there we scored early and had lots of possession, but did not create enough chances. We learned a lot between those two most recent games.
"Hopefully we can use the things we've learned, even if they have changed a lot since then."
Liverpool have failed to win any of their four Champions League matches against Atletico, drawing two and losing two – only Basel have they faced as often without winning in their European Cup history.
Reds defender Virgil van Dijk played a full part in the last-16 double-header two seasons ago but insists that extra-time heartbreak will not be in his thoughts on Tuesday.
"We don't need any extra motivation," he said. "We are playing in the Champions League, the most prestigious cup in Europe. We want to go out there and show our qualities.
"It's a game we're looking forward to and we know we can get a good result there. It's always a good feeling to play at a full stadium."