Jose Mourinho and Antonio Conte's war of words has continued this week after the Chelsea head coach resisted the suggestion of outside help to resolve the dispute with the Manchester United boss.
Here, Liam Blackburn looks at the history of their feud.
The first meeting between Mourinho and Conte ended in embarrassment for the former as Chelsea won 4-0.
The Italian's touchline antics appeared to irk the Portuguese as he said something in Conte's ear after the final whistle.
Reports in the Italian media suggested Mourinho told Conte: "You don't celebrate like that at 4-0, you can do it at 1-0, otherwise it's humiliating for us".
Neither boss divulged what was said but Conte told Sky Italia: "I've been a player too and I know how to behave."
Another Stamford Bridge encounter, another spiky exchange between the two, who had to be separated after Marcos Alonso was fouled.
Ander Herrera was sent off for two yellow cards picked up in tackles made on Eden Hazard, and Blues boss Conte was livid with what he perceived to be a deliberate ploy against the Belgian: "A tactic to play and go to kick an opponent? It's not football for me," he said.
Mourinho was called 'Judas' by a section of the Stamford Bridge crowd.
Responding in his post-match media conference, the Portuguese, Chelsea's most successful manager, said: "They can call me what they want. Until the moment they have a manager that wins four Premier Leagues for them, I'm the number one.
"When they have somebody that wins four Premier Leagues for them, I become number two. Until this moment Judas is number one."
Conte aimed another dig in the direction of Mourinho and Manchester City manager Pep Guardiola as his team closed on their title triumph.
"This season it's very important to understand that it's not always about who spends more money who wins," he said.
"This season isn't the only season both Manchester clubs have spent a lot of money. Look at the past. It's right for them to do this, to reinforce their teams, if they think this is the right way to win the title. (But) every single club decides their own strategy."
Chelsea entered the new campaign knowing the last time they tried to defend their title, under Mourinho, it ended in disastrous fashion as they finished 10th having axed the Portuguese in December when they were just one point above the relegation zone.
It was not lost on Conte, who said in quotes published on espn.co.uk: "We know the difficulty of the next season and for sure we want to avoid the Mourinho season with Chelsea. Two years ago the team ended the league in 10th place and we want to try to avoid this."
When those comments were put to Mourinho at a press conference in Norway after his team had beaten Valerenga 3-0, he responded with a curious turn of phrase.
"I could answer in many different ways," he said. "But I'm not going to lose my hair to speak about Antonio Conte."
The Italian had a visibly receding hairline towards the end of his playing career but now boasts flowing locks.
Mourinho got under Conte's skin when he made a remark about his rivals bemoaning their lengthy injury lists.
Without specifically stating who he was referring to, the United boss said: "Other managers, they cry, they cry, they cry when some player is injured. I don't cry."
Conte was rubbed up the wrong way, and hit back by saying: "A lot of time Mourinho has to see what happens at Chelsea. A lot of time, also last season. I think he has to think about his team and stop... to look at himself, not the others."
New year, same story.
Mourinho's claim he did not need to behave like "a clown" during games to show his passion was treated as a personal affront by Conte, who is known for his touchline exuberance.
Chelsea's boss bit back by suggesting Mourinho had "demenza senile", which translates to senile dementia.
In response, Mourinho appeared to make a pointed reference to match-fixing.
"What never happened to me and will never happen to me is to be suspended for match-fixing," he said.
Conte served a four-month ban following accusations he failed to report his knowledge of an incident of attempted match-fixing in 2011.
He was later acquitted of any wrongdoing.
Conte again hit back, calling the Portuguese a "fake" after an apparent show of support to sacked Leicester boss Claudio Ranieri and a "little man" for his match-fixing comments.
The Italian stood by those comments a few days later at his pre-Carabao Cup semi-final press conference, vowing that he "won't forget" the "serious words" from his rival, and insisting nobody should intervene in the feud.
"This is not a problem for the club," he said. "It's a problem between me and him. Now I stop. Stop."