Manchester City and Pep Guardiola have a Champions League score to settle against Thomas Tuchel, when the newly-appointed Bayern Munich boss visits the Etihad in Tuesday's quarterfinal, first leg.
Tuchel emerged victorious as Chelsea manager in City's first, and so far only, run to the Champions League final in 2021.
That was also the closest Guardiola has come in 10 tries during spells at Barcelona, Bayern and City to land his third European Cup as a coach.
Chelsea's 1-0 win in front of largely empty Estadio do Dragao in Porto due to coronavirus restrictions two years ago was a case of the apprentice outshining the master.
As a young coach Tuchel studied and admired Guardiola's dominant Barcelona side that won 14 trophies in four years from 2008 to 2012, including two Champions League titles.
Their paths then crossed during Guardiola's three years in charge at Bayern, while Tuchel was coach of Mainz and then Borussia Dortmund.
Two football obsessives, the pair even talked long into the night at a Munich bar in 2014, using glasses and salt and pepper shakers to mimic formations.
"I was such a huge admirer of Pep when he was a player and then when he became a coach it was like learning on the job for me," said Tuchel prior to the 2021 Champions League final.
"I was an academy coach and then in the Bundesliga with Mainz, but I don't think I missed a game (of Guardiola's Barcelona) because there was so much to learn."
The respect is mutual. Guardiola described Tuchel last season as "one of the few managers I learn from to develop (into) a better manager myself."
CHAMPIONS LEAGUE PEDIGREE
Guardiola has tended to have the upper hand in clashes between the two.
Three Chelsea wins in the space of six weeks towards the end of the 2020/21 season are Tuchel's only victories in 10 meetings between the two to Guardiola's six.
But he won the most important one and his Champions League pedigree played a large part in Bayern's swoop to secure his services and sack Julian Nagelsmann in a shock move last month.
Tuchel also took Paris Saint-Germain to their maiden final in Europe's premier club competition in 2020 and took eventual winners Real Madrid to extra-time in the quarterfinals last year despite Chelsea being thrust into crisis by sanctions imposed on then owner Roman Abramovich.
The 49-year-old now has the challenge of succeeding where Guardiola failed in leading Bayern back to Champions League glory.
But the weight of expectation falls much more heavily on the City boss.
In his seventh season in Manchester, Guardiola is in the running for his fifth Premier League title.
Yet the failure to get over the line in Europe remains a blot on his copybook.
"It doesn't mean I agree with that but absolutely we will be judged by this competition," said Guardiola on the importance of winning the Champions League to his legacy at the Etihad.
The presence of Erling Haaland adds even more pressure on Guardiola to finally get the job done this year.
The Norwegian scored twice on his return from injury in a 4-1 win at Southampton on Saturday to take his tally for the season to 44.
Those numbers saw Guardiola draw comparisons between his star striker, Cristiano Ronaldo and Lionel Messi.
But it was to make the difference when the fine margins count most in the latter stages of the Champions League that forced City to fight off competition from around Europe to land Haaland.
The 22-year-old has scored 33 goals in 25 Champions League appearances, including five in a 7-0 rout of RB Leipzig in the last 16.