Jose Mourinho and Pep Guardiola will barely be able to muster a handshake when they meet on the Old Trafford touchline on Saturday afternoon but there was a time when the two did not hesitate to embrace.
It has been almost 20 years since the pair shared a city, when Guardiola formed a part of the Barcelona first-team squad and Mourinho was, by name, Sir Bobby Robson's translator.
As we all know, Mourinho had much grander ambitions than simply conveying Robson's message to the players in their native Catalan and would eventually go on to surpass all but a few managers in world football.
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And while Guardiola could be forgiven for not knowing they had a managerial mastermind in the making in their ranks, he did at least know that the young Portuguese man, with no past achievement in the professional game, was a special talent.
Ciaran Kelly, who wrote the biography 'Jose Mourinho: The Rise of the Translator', has detailed how their relationship blossomed between 1996 and 1997, culminating in a touchline hug that any photographer would move mountains to capture in the modern day.
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Writing in the Manchester Evening News, Kelly writes how Mourinho was originally brought to Camp Nou to act as Robson's "eyes and ears" in the dressing room. The English manager, taking over from Johan Cruyff, feared revolution.
Mourinho was acutely aware that his lack of a playing career might hold him back so he decided to make up for it by playing up his strengths. His incredible attention to detail and unstoppable determination to succeed was the only hope he had of winning over a dressing room full of egos.
Not satisfied with his role as El Traductor, Mourinho poured over hours and hours of VHS tapes to analyse each and every one of Barcelona's upcoming opponents. He would deliver dossiers to the relevant players and word quickly spread that Mourinho was much more than a linguist.
Before the help of YouTube videos and digital files, it was revolutionary to have that much data available prior to a match and it quickly paid dividends.
The pivotal moment in question came after Barcelona won the 1997 Cup Winners' Cup, beating PSG in Rotterdam in what was their first European trophy in six years. Guardiola was being led to the Barcelona fans by his team-mates but he escaped and ran towards none other than Mourinho himself.
They embraced in what would be their first and last public display of affection.
When Guardiola's Manchester City arrive at Old Trafford, Mourinho will not only stand with him as an equal but as an archrival. Photographers will be hoping to steal a cold glance or, at best, a heated exchange of words. But a hug, well, surely that is out of the question.