Ahead of Liverpool's Premier League clash with Manchester United at Anfield on Monday Night Football, we examine Jurgen Klopp and Jose Mourinho's head-to-head record.
Monday's much-anticipated encounter on Merseyside, though, will be the first time the duo have met in their current guises as managers of Liverpool and United.
So, who holds the upper hand between the German and the Portuguese?
Borussia Dortmund 2-1 Real Madrid (Champions League Group D, October 2012)
The first time Klopp and Mourinho went head-to-head was in a Champions League group stage clash four years ago while in charge of Borussia Dortmund and Real Madrid respectively.
The former took the spoils on this occasion after his side edged a thrilling encounter at the Westfalenstadion thanks to strikes either side of half-time from forward Robert Lewandowski and left-back Marcel Schmelzer, sandwiched in between Cristiano Ronaldo's customary Real goal.
After the game, Klopp gave an insight into his tactics against Mourinho sides when saying: "They had more of the ball… but that was not a bad thing for us."
Real Madrid 2-2 Borussia Dortmund (Champions League Group D, November 2012)
The two managers did not have long to wait before coming up against each other again as Madrid entertained Dortmund in their next Champions League Group D contest at the Santiago Bernabeu.
However, the 'Special One' was still left waiting for his first win over Klopp after a 2-2 draw in the Spanish capital, with Los Blancos grateful to Mesut Ozil's last-minute free kick rescuing them a point.
Nonetheless, Mourinho was given notice of what to expect in any future meetings with Klopp-managed teams after a pulsating first half from the Bundesliga champions had seen them deservedly lead 2-1 at the break.
And while both went on to qualify from the group, it was Klopp who earned the bragging rights after his team topped the section ahead of Real.
Borussia Dortmund 4-1 Real Madrid (Champions League semi-final first leg, April 2013)
Five months later and the two super coaches were once again plotting each other's downfall, with a place in that season's Champions League final at Wembley Stadium at stake for the victor.
Back in front of Dortmund's Yellow Wall, though, the Portuguese's team were annihilated after a four-goal blitz from Lewandowski, and this despite the tie still being level with 40 minutes to go.
Real Madrid 2-0 Borussia Dortmund (Champions League semi-final second leg, April 2013)
"I have said a little bit about Dortmund and that's enough," said Mourinho ahead of the match. "Since the day of the draw, Klopp talks every day."
The Dortmund boss was unperturbed, though, responding: "Mourinho says I speak too much? That's what one of my teachers used to tell me. I don't care, I don't think about this."
And when asked whether this was mind games, Klopp added: "I'm not intelligent enough to understand what it should be. But it's no problem, now I'll shut up, and everything is okay."
Despite Mourinho recording his first victory over the all-smiling German at his fourth attempt, courtesy of late goals from Karim Benzema and Sergio Ramos, it was a bittersweet moment as Klopp's men still edged Real 4-3 on aggregate to progress to the final against Bayern Munich.
And by the end of that campaign, Madrid and Mourinho had also parted company…
Chelsea 1-3 Liverpool (Premier League, October 2015)
Klopp made it three wins from five encounters with Mourinho after getting the better of the-then Chelsea manager to register his first victory as Liverpool boss last October.
At the time, the champions were struggling near the foot of the table having lost five of their opening 10 league fixtures and Klopp increased the pressure on his rival by inflicting the Blues' sixth defeat of the campaign.
And yet it had all started so well for Mourinho, whose side took an early lead through Ramires, only to then collapse following Philippe Coutinho's brilliant strike in first-half injury time.
Further goals followed after the break from the Brazil playmaker and Christian Benteke, with Klopp even finding time to sympathise with his beaten opponent after the game.
"Things like this happen," he said. "I had a similar situation at Dortmund last year. The good thing was no one in the club was in doubt of my situation. I feel for him of course, but it's work."