Liverpool boss Jurgen Klopp was left fuming after Sunderland midfielder Jeremain Lens escaped a red card for a challenge on Mamadou Sakho, though his counterpart Sam Allardyce disagreed, calling Klopp a "soft German."
Netherlands international Lens careered wildly into Sakho in an ugly clash as time ran down during the Reds' 1-0 Premier League victory at the Stadium of Light on Wednesday evening, and was only booked by referee Kevin Friend.
However, Klopp, whose staff became involved in heated exchanges with their Black Cats counterparts on the sideline in the aftermath, insisted Lens should have been dismissed.
"I don't want to say now, 'Come on, give him a red card.' I have no problem with this player, but if you go like that, everything can happen," Klopp said. "That's not allowed. For me, that's a red card, finish, that's it."
Asked if Sakho had escaped serious injury in the incident, Klopp added: "I hope so, yes. But we cannot decide and say, 'OK, nothing serious happened and it's nothing.'
"A lot of small things, they got yellow cards and you think, 'Why?' and this is a yellow card too? It's not how it should be. But it's over, it's OK, there's nothing to talk about."
Sunderland boss Sam Allardyce, however, was of a markedly different opinion, saying with tongue firmly in cheek: "He's a soft German. It's not a red card, it's a yellow. It's a foul."
Asked about the verbal confrontation on the sideline, Allardyce said: "There was some foul and abusive language towards my staff that I didn't like. After the end, it was all right, though because we all shook hands and got on with it, which is what we have got to do."
For Allardyce's men, it was a fifth successive defeat, which leaves them seven points adrift of safety and facing a massive bottom-of-the-table clash with Aston Villa on Wearside on Saturday.
Asked to sum up December, the 61-year-old replied succinctly with a one-word expletive.
"This is against Liverpool, it's £250 million, £300m worth of talent they are playing against and in some spells, matched it," Allardyce added. "The only thing we need is somebody to put the ball in back of the net and us to win a game to build the confidence.
"That, for me, means that we have got to face the fact that it can always be that you can lose against Liverpool if you play your best. What you have got to do is play your best against Aston Villa and win."
Meanwhile, Allardyce refused to confirm Lorient defender Lamine Kone is close to sealing a switch to Sunderland despite the French club revealing a fee has been agreed.