Maurizio Sarri watched Claudio Ranieri's Fiorentina train regularly in the 1990s and returned the favour when his fellow Italian was out of work earlier in the autumn.
Now Sarri's Chelsea will be seeking to bounce back from their first Premier League loss of the season, to Tottenham Hotspur last Saturday, against Ranieri's Fulham at Stamford Bridge on Sunday.
Ranieri - sacked by Leicester City nine months after their title success and having had a season-long stint at Nantes in Ligue 1 - was twiddling his thumbs when he visited Sarri and his former Chelsea player Gianfranco Zola at the Blues' Cobham training ground.
"I spoke with him for three days - I don't remember exactly - one month ago, or 45 days ago," said Sarri, who said they dined together only in the Chelsea training ground canteen.
"He came to Cobham to see two, three trainings. He wanted to speak with me, with Gianfranco."
Sarri does not expect the 67-year-old Ranieri, who won his first match as Fulham manager last Saturday against Southampton, will recall having hosted him when he was working in a bank while also coaching Tuscan amateurs Antella.
That was a few years before Ranieri was appointed Chelsea manager, in September 2000 for a four-year stint which ended when owner Roman Abramovich appointed Jose Mourinho.
The 59-year-old former Napoli manager said: "I went to speak to him when he was the coach of Fiorentina, 20 years ago, maybe. I don't remember very well, but I don't think he can remember this meeting."
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Asked if he was worried Ranieri would recall his own methods, given the more recent experience, Sarri added: "But I saw his training 20 years ago.
"Usually a team of Claudio is really very solid. They usually defend very well, sometimes low, but very well. Usually he has a team very dangerous at counter-attacks, like in Leicester, but not only in Leicester."
Sarri would not call Ranieri a friend - "friend is a big word, I think, but I like him very much," Sarri said - but found it difficult to fathom why big clubs did not make offers for Ranieri following his exploits with Leicester in 2015/16.
"Usually the presidents are very strange," he said.
He more understood Ranieri's frustrations at being out of work, before Fulham called.
Sarri added: "Usually you can live very well for two, three months, then you're in trouble.
"Every coach, I think, is like this. For two months you're happy because you have time, and after two months you miss adrenaline."
Ranieri was adamant no amount of time behind the scenes with Sarri would give the Cottagers any pivotal advantage.
When asked what he learned from spending time at Chelsea as Sarri's guest, Ranieri replied: "I know everything, but believe me it's difficult to stop them.
"I asked, and Maurizio invited me. I was there one week and we had lunch after the training session.
"He was very kind. We spoke normally but when I don't have a job I often go around and watch all the teams.
"I also went to watch [Jurgen] Klopp at Borussia Dortmund.
"I don't want to stay at home. I look and I go around the world; it's important to look at what's happening."
Before last week's setback against Tottenham, Chelsea were one of only three teams unbeaten in the Premier League, alongside leaders Manchester City and Liverpool. Ranieri praised his compatriot for the start he has made to life in England, but refused to take any credit for it.
"Sarri plays very well with the right philosophy; Sarriball," Ranieri said. "But I think Sarri is not inspired by me, he's a very good coach, because he arrived so late at the highest level.
"He deserves it. He has a lot of jobs in his career, and he deserves where he is."