When Chelsea take on Manuel Pellegrini and his Real Betis side on Wednesday night, they will be facing a manager with a bigger influence on the Blues than some may think.
Around 15 years ago, Pellegrini was managing in Malaga when he spotted one of his players, in his 30s, with an eye for the game - and told him to pursue a career in coaching.
His name was Enzo Maresca.
"You can often tell which players might go on to be good coaches - from the impression they have on others, how they absorb concepts in training," said Pellegrini recently.
"With both Enzo and Willy [Caballero, Chelsea assistant coach], I was sure they'd go on to become influential coaches on a global level."
In a twist of fate, Pellegrini is one step away from delivering Betis a first European title - but the manager in his way is one he helped to create.
Not only did Maresca become a coach, but Pellegrini took the Italian under his wing as an assistant at West Ham - and still mentors him to this day.
"I define him like a professional dad because when I need to make big decisions, we are in contact," said Maresca this month, who then went on to say he was speaking to Pellegrini about coaching issues as recently as last week.
You wonder how many of Chelsea's problems Maresca has revealed to Pellegrini this season.
Pellegrini not only pushed Maresca into the coaching world but he also developed him - right up to the point of eventually taking a job like Chelsea.
"I learned a lot from him, especially how to manage players, how to manage a squad," added Maresca. That will have come in useful at Chelsea given the number of players they have signed in recent years.
Now there is a sense of unity at Chelsea - resulting in their qualification for the Champions League.
Maresca and Pellegrini are not only linked historically but philosophically as well. There are certain similarities between the two managers - no better linked than their views on offside.
At Chelsea this season, Maresca has used the tactic commonly known as the 'Pellegrini offside trap' - playing a high line on the edge of their own penalty area, in an aggressive way of defending.
Maresca's deployment of this tactic at Chelsea has been well-noticed - but not always in a positive light, as the better sides have used the Blues' method to their own advantage.
Liverpool, Arsenal and Newcastle - three out of the Premier League's top five - have all scored goals against Chelsea this season by successfully beating that offside trap. Aston Villa also beat it in the 2-1 win over the Blues at Villa Park.
But while there are negatives - showing how far Maresca has to go to become the title-winning coach Pellegrini was in England - there are plenty of positives too. And the offside trap can work.
Only Liverpool and Villa caught their opponents offside more times than Chelsea in the Premier League season just gone, highlighting how effective Maresca learning from Pellegrini can be.
Maresca has faced his critics at Chelsea this season but as his debut campaign reaches its close, the Italian has ended up being a 'right place, right time' type of manager.
His experience of coaching Manchester City's B team - where he worked with the likes of Cole Palmer and Romeo Lavia - helped get results with the youngest squad in Premier League history.
His time working as Pep Guardiola's assistant at City has helped him at Chelsea too. The inverted full-back tactic that Guardiola brought to England has created positive career progression arcs with the likes of Marc Cucurella and a resurgent Reece James.
Don't forget his playing days as a midfielder, where he even scored twice for Sevilla in a European final against Middlesbrough in 2004. His input has helped Moises Caicedo and Enzo Fernandez to start to justify the eye-watering fees Chelsea mustered for the pair.
But getting results and progressing players is one thing - turning them into winners is another.
Getting hands on a trophy, something the Blues have not done since 2021 - the year they won the Champions League and Club World Cup - would be a big step in not just Maresca's project, but the Todd Boehly and Clearlake Capital one too.
To do that, Maresca has to beat his mentor. With all the influences the Chilean coach has had on his career, all roads seem to lead towards Pellegrini.