Jurgen Klopp's side stormed into a 2-0 lead at Anfield thanks to goals from Diogo Jota and Sadio Mane, with Trent Alexander-Arnold grabbing both assists.
But the major talking point came just before the interval, when Atletico centre-back Felipe was sent off by the official.
The Brazilian was initially set to be booked for a very cynical foul on Mane near the halfway line, but then saw the yellow upgraded to a red card because he appeared to ignore referee Danny Makkelie.
Honestly, we're not joking...
Video: Felipe's ridiculous red card vs Liverpool
Have you ever seen anything like it in a high-profile professional match?! During the second half, the BT Sport commentators revealed that UEFA's stance was that Felipe was sent off solely for the reckless challenge.
Make of that what you will...
Luis Suarez and Koke were both shown yellow cards for protesting the decision to dismiss their teammate from the pitch.
It really was absolute mayhem.
Diego Simeone's men completely lost their heads towards the end of the first half at Anfield and were lucky to go in at the break with 10 players still on the field.
In the fixture featuring the two teams at the Wanda Metropolitano two weeks ago, Atletico also picked up a red card due to Antoine Griezmann's reckless high foot on Roberto Firmino.
The Spanish side's discipline against Liverpool could prove very costly to their Champions League ambitions this season...News Now - Sport News