Diego Simeone opted not to shake Jurgen Klopp's hand after Liverpool's Champions League win over Atletico Madrid, with the Rojiblancos boss darting down the tunnel as soon as the final whistle sounded.
The Reds escaped their trip to Spain with a 3-2 victory, taking advantage of Antoine Greizmann's red card before Mohamed Salah converted from the spot in the second half to break the deadlock.
Atleti, meanwhile, were denied a penalty of their own moments later and, as the match ended, Simeone opted to head straight to the dressing room, leaving Klopp without a post-game handshake and the German yelling down the tunnel.
What was said?
"We don't like that, but yes, the situation is clear," Klopp told BT Sport. "I want to shake his hand. His reaction for sure, like mine, was not so cool.
"The next time we see each other we will definitely shake hands. It's nothing. He was obviously angry, not with me but with the game. There is nothing else."
Simeone explained the incident as a mere miscommunication, as he generally doesn't do handshakes after matches.
“I never shake hands after a match, because I don’t like it," he said. "It isn’t healthy for either the one who wins or the one who loses. That’s the way I see it.
"But now when I see him I will shake his hand without problem.”
Controversial calls
Tuesday's clash was fairly controversial, with both teams on differing sides of the penalty process across two separate incidents.
Liverpool, of course, were awarded a spot-kick after Mario Hermoso brought down Diogo Jota in the box, paving the way for Salah's game-winner.
But, in the 82nd minute, Jose Maria Gimenez was bumped down in the box by Jota, prompting the referee to award a penalty. However, after a VAR review, that call was changed as no foul was given.
Atleti with decade-worst defensive performance
Atletico Madrid conceded two goals in the opening minutes, with Salah and Naby Keita firing Liverpool into the lead within 13 minutes.
The two goals sealed an unfortunate record for Atleti, who had never conceded twice so quickly in the Champions League.
In fact, Tuesday was the first time Atleti had conceded more than twice in a Champions League home game under Diego Simeone, having last done so in December 2009 against Porto under Quique Sanchez Flores.