Liverpool turned in a poor display as they were beaten by Real Madrid in their Champions League quarter-final first leg on Tuesday evening.
The Reds travelled to Spain on the back of an impressive display against Arsenal in the Premier League.
But they were well beaten in Madrid.
The home side lead 2-0 at half-time courtesy of goals from Vinicius Junior and Marco Asensio.
Mohamed Salah pulled one back shortly after the break, only for Vinicius Jr to score his second with 25 minutes remaining.
There were no further goals, meaning Liverpool will have to overturn a two-goal deficit in the second leg.
Jurgen Klopp was not happy at the final whistle.
He confronted referee Felix Brych as the two sides made their way off the pitch.
Per Sky Sports Germany, Klopp said in German: "That's bad! Just unfair!"
While Brych hit back, replying: "What you're doing now is unfair, too."
So, what was Klopp so angry about?
He explained in his post-match interview that it was to do with a lack of action taken over the treatment of Sadio Mane.
The Senegalese went to ground multiple times on the evening but, on numerous occasions, was not given a foul.
Klopp accused Brych of making 'personal' decisions against Mane.
“The situation with Sadio, I have to say what the referee did tonight I don’t understand. For me that was something personal, because he dealt with the situation with Sadio, which is a clear foul, like it was a dive or something," he said, per Goal.
"And from that moment whenever Sadio went down, he couldn’t get anything anymore. That’s just not right
“That’s what I told him after the game, that I just thought he was unfair with Sadio, and that’s how it is.
“It doesn’t change anything at all. He didn’t lose the game, we were not good enough, but in these moments you need just an OK ref. That would have been enough.”
Klopp will be hoping his side put in a much better performance in the second leg at Anfield next week.