Lopetegui will hope he knows exactly what he is coming up against at the Ramon Sanchez-Pizjuan as Machin disclosed one of his tactics to his opposite number in a meeting seven months ago.
The former Spain boss was in preparation mode heading into the World Cup and wanted to know how to counter the three-at-the-back system which teams such as eventual semi-finalists Belgium and England would be using at the tournament.
Lopetegui attended the Liga fixture between Girona and Celta Vigo in February, and took the opportunity to meet up with Machin.
In addition to gaining insight on how to play against teams operating with three at the back, Lopetegui also sought to understand its implementation for his own purposes. It is why he named eight defenders in his squad for the World Cup before he was sacked on the eve of Spain's opening game following the announcement of his appointment as Madrid coach.
Lopetegui will now be able to use his knowledge of the tactic and utilise the counter measures he was taught in the meeting with Machin, potentially giving Los Blancos a distinct advantage heading into the Sevilla game.
Machin, who took over at Sevilla in the summer, realises that it may now be a battle to get the better of a man who knows some of his secrets.
“Who would have said that, in the following season, we would be facing each other, with me at Sevilla and he at Madrid,” said Machin.
“I think we both would have signed up to it (if Machin and Lopetegui had been offered the chance to coach Sevilla and Madrid, respectively).
“I gave my point of view on this system, but ideas and theories are one thing, reality is another.”
However, Machin has faith in his squad, adding it is still down to the players to win or lose the game.
“We can’t forget that the protagonists are the players and their qualities are what make you win or lose," he added. "Coaches help, but those who score goals or save them are key.”
It would come as a massive shock if Machin ditched his system for the Madrid game, but it remains to be seen how well Lopetegui took notes on how to break down this Sevilla side who rarely take a beating at home.