Liverpool coach Juergen Klopp railed against Atletico Madrid's negative tactics and gamesmanship after the holders fell to a 1-0 defeat away from home in a tense Champions League last-16 first leg in the Spanish capital on Tuesday.
Saul Niguez's scrappy goal in the fourth minute got Atletico off to an ideal start in a fervent atmosphere at the Wanda Metropolitano but Klopp was unhappy with some aspects of Diego Simeone's side's play.
"You need to be really strong as a referee in this atmosphere. Already in the first 30 minutes three of their players went to the ground, I don't know what for," Klopp told reporters.
"They got a result, the stadium wasn't here to see sensational football. Atletico were here to squeeze a result out of this game, they got the result and so they are happy and we are not that happy."
The biggest flashpoint of a fiery game saw Atletico loudly appeal for Liverpool forward Sadio Mane to be sent off for a second clash with Sime Vrsaljko after being booked for an earlier incident with the Croatian.
Klopp substituted the Senegal international immediately after the interval.
"The plan today was to get Sadio out of the game with a yellow card, I was a bit afraid that his opponent would go down if Sadio only takes a deep breath or whatever," added Klopp, who was himself given a booking for protesting on the sidelines.
"I didn't want to have that situation and that's why I took him off. He was targeted. It was clear. It's part of football but I don't like it."
The German coach has overseen a number of inspiring second-leg comebacks in European matches at Anfield and warned Atletico what awaited them on Merseyside next month.
"As long as we can get 11 players in a Liverpool shirt we will try with all we have. For all Atletico fans who have got a ticket, welcome to Anfield," he added.
"It's halftime, we're 1-0 down, we wouldn't give up if we had 15 minutes of half time so why should we when we have three weeks, and even better, the second half will be played in our stadium."