Chelsea star Enzo Fernandez was seen taunting Mason Mount after his side's late comeback win against Manchester United.
On Thursday night, the Blues scored two goals deep into added time to turn the game on its head and claim a 4-3 victory over their rivals at Stamford Bridge.
United were leading the game up until the 99th minute before Mauricio Pochettino's side struck twice late on - making it the latest comeback in league history.
Mount, who made his return from a calf injury last month, was making his first appearance in west London since leaving to join United for £60m in the summer.
It was clear that there was a degree of resentment towards Mount - who came through Chelsea's academy and made 195 appearances for the first team - as players and fans alike made their feelings known.
In a video that emerged on X, formerly known as Twitter, Chelsea midfielder Enzo Fernandez could be seen taunting the United midfielder after the final whistle.
A clip showed the Argentine, during his immediate post-match celebrations, turning towards Mount and smacking the Chelsea badge on his chest.
He also appeared to say something to the midfielder, though it remains unclear as to what was said.
Moreover, during the game, Fernandez was seen clashing with Mount - with fans suggesting he was trying to 'trigger a reaction' from the United midfielder.
In a separate clip, Fernandez can be seen kicking the ball at Mount with the two players going head-to-head before eventually being separated.
As Mount walked away, he appeared to yell something in the direction of the 2022 World Cup winner as tempers began to boil over.
Interestingly, Mount and Fernandez were teammates for half of the 2022-23 season - after the latter's arrival during the January transfer window.
Earlier in the game, TNT Sports cameras caught the moment when a Chelsea fan lifted a 2021-22 edition of their home shirt which read 'JUDAS 19'.
Though Mount wears the number 7 for United, during his Chelsea days, he wore the number 19 - making it a clear reference by the home supporters.
The 25-year-old came on as a late substitute in the match - when United were leading the match - and was met by a chorus of boos from home supporters.
It was a night to forget for Mount, who spent four full seasons at Chelsea, as he watched his side capitulate deep into added time at Stamford Bridge.
Erik ten Hag's side showed brilliant powers of recovery to lead in west London in the closing stages, having gone behind to two early goals by the Blues.
But with the finish line in sight, Diogo Dalot conceded a late penalty, which was dispatched by Cole Palmer, before the visitors switched off and allowed the former Manchester City winger to complete his hat-trick from a quickly-taken corner.
The winger's three-goal haul on the night brought Palmer joint-second in the race for the Golden Boot with 16 goals, just two behind Erling Haaland.
