Christensen put his side in serious trouble with a red card just before half-time before under-fire goalkeeper Kepa gifted Sadio Mane a goal with a disastrous pass in the second half.
With the match scoreless as half-time neared, Jordan Henderson picked out Mane with a driven long ball and the forward found himself behind Chelsea's defence.
As Kepa charged off his line, Christensen took matters into his own hands.
The Danish defender took down Mane with a rugby tackle, putting his arms around the Senegal star and wrestling him to the ground before he reached the ball.
Referee Paul Tierney originally showed Christensen a yellow card but then went to the monitor to check if the defender had denied an obvious goalscoring opportunity.
After a VAR check, Tierney changed the colour of Christensen's card from yellow to red and Chelsea paid the price five minutes after the break when Mane headed the visitors into the lead.
There was plenty of reaction on social media to Christensen's red card.
Andreas Christensen saw Kepa in goal and panicked.— Shirtless Plantain Show (@Nigerianscamsss) September 20, 2020
2009 - Andreas Christensen is the first player to be sent off in a Premier League fixture between Chelsea and Liverpool since Frank Lampard in February 2009. Orders. pic.twitter.com/Hz7kHEOklW— OptaJoe (@OptaJoe) September 20, 2020
Christensen trying to bring Mane down like pic.twitter.com/24GRDbhNjy— ODDSbible (@ODDSbible) September 20, 2020
That's what VAR should be used for. Clear and obvious. Christensen had both arms around Mane, clear denial of goalscoring opportunity, never a yellow, had to be red. VAR Oliver intervened, encouraged Tierney to check monitor (hallelujah) red replaced yellow, system worked #CHELIV— Henry Winter (@henrywinter) September 20, 2020
That’s just not smart from Christensen. Very poor. He’s bear-hugged Mané when he absolutely didn’t need to.— Alex Goldberg (@AlexGoldberg_) September 20, 2020
Thiago Silva in for him from here on out, please.
This is the very reason I dislike Christensen. What’s the point in playing extremely well one game to start rugby tackling a player to get sent off in the next? Poor. Stupid. Mané would’ve still had a lot to do to get past Kepa and score. Thiago Silva can’t play soon enough.— CFC DUBois (@CFCDUBois) September 20, 2020
On the red card as well, props to the officials for noting that, if anything, Kepa potentially reaching the ball before Mane makes it even more of a clear goalscoring opportunity— FootballJOE (@FootballJOE) September 20, 2020
Chelsea's afternoon went from bad to worse in the 54th minute when Kepa took a routine pass and played the ball directly to Mane's feet, gifting the forward a second goal on the afternoon.
That would be all Liverpool needed on the afternoon as the defending champions cruised to a 2-0 win.
With Rennes goalkeeper Edouard Mendy closing in on a move to Chelsea, there was plenty of speculation that the error-prone Kepa could be set for an indefinite spell on the bench.
Kepa. World's most expensive goalkeeper disintegrating into a puddle of his own self-confidence with the world watching. The position can be one of the most lonely and psychologically damaging in sports. Getting to the point where begin to worry for the 25-year old— roger bennett (@rogbennett) September 20, 2020
Kepa just threw his gloves angrily into the stands after conceding that goal, one of the Chelsea ball boys threw them back... he still didn’t manage to catch them.— Footy Humour (@FootyHumour) September 20, 2020
Awful from Kepa but Mane's work rate is relentless. Angry with himself for misplacing a pass and desperate to make amends, shuts down the keeper and bags his second of the day. #LFC— James Pearce (@JamesPearceLFC) September 20, 2020
Edouard Mendy's price tag has just increased by £20m after that Kepa mistake pic.twitter.com/1XbrbaGf7c— ODDSbible (@ODDSbible) September 20, 2020
Kepa Arrizabalaga is the worst goalkeeper I’ve ever seen in the Premier League and I’m not even exaggerating.— Transfer News (@TransferChecker) September 20, 2020
By no means am I trying to rag on the guy, but if we are being honest, Chelsea pretty much start every game 1-0 down when Kepa starts.— Alex Goldberg (@AlexGoldberg_) September 20, 2020
I don’t want to say anything bad about Kepa but I think that mistake for Liverpool’s 2nd goal could be his last involvement with the team for some time. #CHELIV— Frank Khalid (@FrankKhalidUK) September 20, 2020