Marc Cucurella was shown a red card after the full-time whistle during Chelsea's win over Brentford, with the Premier League now revealing why.
Chelsea came out 2-1 winners over their west London rivals on Sunday night, with Cucurella netting the opener.
Nicolas Jackson doubled Chelsea's lead with 10 minutes to go before Bryan Mbeumo seized on an error at the back to make the ending nervy at Stamford Bridge.
With just minutes to go in added time, Cucurella was given a yellow card for a rash challenge before Christian Norgaard pulled the Spaniard to the floor and was also cautioned.
As the referee blew the full-time whistle and three points were secured, Cucurella was handed a second yellow card.
The left-back, who has been in fine form this season, scored his first Premier League goal for Chelsea but also received his first red card in the competition and the reason he was sent off has now been revealed.
Cucurella netted the opener for Chelsea before eventually being sent off.
Cucurella netted the opener for Chelsea before eventually being sent off. / IMAGO / Action Plus
Speaking after the match, Enzo Maresca admitted that he was too busy celebrating to see what happened as he said: When the final whistle (went), I was celebrating so I did not see nothing."
Many of the Stamford Bridge faithful will be in the same boat as Maresca, with Chelsea closing the gap to Liverpool at the top of the Premier League to just two points.
However, those watching at home saw exactly what happened upon the end of the match as Cucurella got into it with the Brentford players and the match officials.
An official statement from the Premier League wrote: "The referee issued a second yellow card to Cucurella for adopting an aggressive attitude. Schade was also booked for the same offence."
While many Chelsea supporters will disagree with the referee's call, Brentford boss Thomas Frank thinks that the official made the right decision as he criticised Cucurella for his role in Norgaard's yellow card.
"I think Cucurella is a top player, he is doing well," Frank said. "But I don't like it when players go to the ground and holding their face. I will say to Cucurella because I respect him massively."
Chelsea will be without their key player when they look to go top of the Premier League next weekend at Goodison Park.
The Blues face Everton a few hours before Liverpool take on Tottenham Hotspur, with the chance to leapfrog Arne Slot's men.