When fans think of Leinster Rugby, both Johnny Sexton and Leo Cullen are among the first names that come to mind.
The former is arguably the greatest ever player to don the blue jersey, steering the province to four Champions Cup titles from out-half among a plethora of other trophies.
Cullen, meanwhile, captained the side in three of those major European successes before becoming the first ever man to win it both as a player and a head coach when Leinster added their fourth star in 2018.
They're both Leinster legends; their dispositions on the pitch couldn't be more different
The duo enjoyed a healthy partnership throughout their professional careers although, according to Sexton, things did go astray during a training session in their playing days.
It was on international duty as opposed to under the Leinster umbrella, when both men had been selected as a part of the Ireland squad for the 2011 World Cup.
At the tournament, the competition between Sexton and O'Gara for the Ireland #10 shirt was its most competitive. Sexton had overtaken O'Gara that year, but the Munster outhalf, being the dogged competitor he is, was not going to lie down.
It was a fierce - and borderline toxic - rivalry, as some former Ireland internationals have explained.
Sexton had started the game when Ireland stunned Tri Nations champions Australia 15-6, but had a poor day on the kicking tee with out-half rival Ronan O'Gara closing out the win and regaining the starting berth in the process.
Sexton was dropped for Ireland's subsequent demolition of Russia and head coach Declan Kidney looked ready to persisted with the Cork native for their clash with Italy - a call a frustrated Sexton had anticipated.
Sexton, writing in his new book Obsessed, explains how lost his cool during a training session in Dunedin on the eve of that game. It was an A v B game and Sexton was with the B team.
However, it was Cullen as opposed to O'Gara who found himself on the receiving end of his anger.
Johnny Sexton recalls training scrap with Leo Cullen
In an extract from his new book Obsessed - which is set to be published next month - from which extracts were featured in the Sunday Times yesterday, Sexton painted the unsavoury scenes which he says he has since apologised for. In the book, he explains how he used to imagine Ronan O'Gara's face on a rugby ball when he was attempting a kick as a means to concentrate.
Having lost his place to O'Gara at the 2011 World Cup, Sexton then lost the plot with Leo Cullen, of all people, on the training ground.
"He grabbed me at a ruck and I slapped his arm away aggressively.
It happened again and I swung again. He slapped me in the face and that’s when the red mist descended. I grabbed him by the collar and started swinging like mad. People tried to drag me back but I lost the rag altogether. I split him open, just above the eye.
"I’m sure I took him by surprise. We were very close, after all. He was my club captain and I had massive respect for him. I’m sure it took everyone by surprise. Not my finest hour."
Citing the fact that 'no one was laughing' at the time, Sexton stressed his shame at what had transpired between him and his captain that day. He also said Cullen accepted his apology.
The former World Player of the Year is renowned for his competitive temper, something which reared its head on numerous occasions during his playing career.
Even as his career came to a halt in Paris last year, he found himself embroiled in a spat with New Zealand's Rieko Ioane after Ireland's loss to the All Blacks in the 2023 Rugby World Cup quarter-final.
He has also documented his perspective on what was actually said between the pair after his prospects of a dream end to his career were halted in the French capital.
