Andoni Iraola criticised referee Chris Kavanagh's decision to send off Ryan Gravenberch for two bookable offences in Liverpool's 3-0 defeat to Manchester City.
Liverpool had been the better side before the Dutch midfielder was dismissed in the 62nd minute for pulling back Jeremy Doku. Gravenberch had earlier been cautioned at the start of the second half for catching Elliott Anderson.
City capitalise on man advantage
Manchester City immediately took advantage of the extra man as quick-fire goals from Erling Haaland and Doku put Enzo Maresca's side in control, before Rayan Cherki completed the scoring.
Speaking after the final whistle, Iraola said he was bemused by the decision to book Gravenberch and insisted the referee made the wrong call.
"I think the first foul of Ryan is never a yellow card, never," he said. "These kinds of games, just a stomp on the big toe, or something minor.
"He doesn't even call the foul straight away. He leaves it go, I think Elliott Andersen does a couple of steps. He decides to go down.
"I don't know why after he shows the yellow card, because it's not a situation where it leaves advantage. We had nine players behind the ball, it was in the middle of the pitch, no danger there.
"And then you put, as a referee, yourself in trouble, and also you put us in trouble."
Consistency questioned
Having seen Gravenberch dismissed after Haaland gestured for a second yellow card, Iraola was also unimpressed at a lack of consistency from Kavanagh after Ronald Araujo had been booked early in the game for the same offence following a handball from Marc Guehi.
"Also at the beginning of the game, yellow card of Ronald," he said. "I know he complains, he does this.
"But in these kinds of games, if you are going to start after a handball of Guehi, the punishment is for Ronald complaining and this.
"You put it straight away at the beginning of the game, the right-back with a yellow card. I think you are in the textbooks, yes, perfect. He complains, you can show a yellow card.
"But then I will be very careful all the season. Every time someone complains, it has to be a yellow card."
