Jurgen Klopp admitted Liverpool should not have been awarded a penalty in Friday's tempestuous 2-1 Merseyside derby victory over Everton, in which debutant Virgil van Dijk scored the winner.
The hosts took the lead at Anfield after Mason Holgate was adjudged to have fouled Adam Lallana, with James Milner converting the consequent spot-kick 10 minutes before half-time.
Reds boss Klopp raged against a similarly questionable call in last month's 1-1 Premier League draw against the Toffees, when Dominic Calvert-Lewin went down under pressure from Dejan Lovren, and he felt the two incidents were comparable.
"It was a similar situation, the first one [in December's match] was no penalty in my opinion and this one wasn't also," he told BBC Sport. "It's the same.
"There is contact and the referee used his whistle. Exactly the same situation."
The match was not short on controversy, with Holgate involved again when he shoved Roberto Firmino in the back to send the Brazilian tumbling into the crowd.
It fell to £75million signing Van Dijk, the world's most expensive defender, to settle it six minutes from time after Gylfi Sigurdsson had equalised and Klopp was happy just to reach the fourth round of the FA Cup.
"It was for sure not the best piece of football for 95 minutes, but a proper fight," said the German. "I'm delighted with the attitude we showed again, it was a difficult game.
"It was not the night for brilliant football, to play through. You would love to see that but Everton defended well. They played football, a big difference to the last game between us to be honest.
"The equaliser was the worst protection I ever saw in my life. It made no sense at all. We were all in the wrong direction. But when you make mistakes in football you have to react and we did again.
"It was nice that Virgil van Dijk could score in his first game, a brilliant header. I am really happy."
On Holgate's push he added: "It was not necessary for Mason Holgate to give Firmino that push, it was really dangerous and usually players don't do that. We cannot change that."