There will, the friends both agree, be a sturdy, heartfelt embrace after the final whistle. Whatever happens through the 90 minutes of intimate rivalry, their closeness will survive undamaged.
It could not be otherwise for Antoine Griezmann and Diego Godin, who over five years as colleagues forged the sort of bond that is rare in their transient profession.
Four months ago, the Frenchman and the Uruguayan were teammates at Atletico Madrid. Both were preparing goodbyes after the greatest adventure of their club careers, at an institution where togetherness had been fundamental.
That they stepped away in tandem, Griezmann to join Barcelona, Godin to sign for Inter Milan - two clubs who collide in the Uefa Champions League on Wednesday - seemed almost inevitable. A year earlier, Godin had been persuasive in keeping his friend in Madrid for one more season. And Griezmann, 28, has always listened to the counsel of Godin, 33, and trusted it.
In some ways, they are unlikely blood brothers, one a dashing forward, figurehead of France’s world champions, who has high-profile sponsorship endorsements and wears his hair long and wavy enough to land advertising contracts for a shampoo firm.
The other is the gnarled centre-half who came to epitomise Atletico’s rugged rise through Europe’s hierarchy over the last decade. Godin does not advertise shampoo: on top of the wise head that has won countless aerial duels, his hair is thinning.
They remain in regular contact. Godin is godfather to Griezmann’s daughter, Mia, and although they can no longer meet up, ad hoc, on days off for a neighbourly barbecue and long conversations, they do share stories of their new workplaces and the challenges around belonging somewhere other than Atletico.
Godin still gives sound advice, just as he did to Griezmann when the then waspish young winger first joined Atletico, from Real Sociedad, and found in Godin a mate for life.
Godin knows Griezmann well enough to sense the pressures his friend’s arrival at Camp Nou have brought to bear. Any €120 million (Dh480m) signing at Barcelona would carry baggage. A recruit who 12 months earlier made an unwisely ostentatious gesture of turning down Barcelona in favour of a fifth season at Atletico - Griezmann released a film of his dilemma, posted online - has even more to prove.
He is doubly obliged to make a swift impact because this Barcelona, who have underachieved in Europe for the past four years, only last weekend put an end to a run of eight away games without a win.
In the dressing-room there are senior players who would have preferred the club’s board to push harder for Neymar to return in the summer than commit so much of the budget to Griezmann’s capture.
Godin believes Griezmann will make a success of Barcelona, once, as at Atletico, he forms strong alliances - notably with Barca’s greatest statesman.
"When Leo Messi recovers full fitness, they will all get better," Godin told Marca. "There's a Barca with Messi, there's a different Barca when he's not there."
Messi’s injury setbacks this season mean he and Griezmann have yet to play more than half a game together. Promisingly, in the one match they started together, Messi set up a Griezmann goal within seven minutes of kick-off.
Less promisingly for Inter, Messi is expected to be fit enough to play a significant part on Wednesday evening, up against an Inter defence where, Godin admits, he does “not yet feel like the leader yet, but then I’m not one to come in and start kicking at the door”.
What he does know is that he was brought in to provide an authority and resilience Inter urgently required. Being new, he is feeling his way, adapting to the back-three formation preferred by manager Antonio Conte, getting used to playing closer to the opposition half.
Against Griezmann’s pace, that will require some pluck; against Griezmann, Messi and Godin’s compatriot and long-term ally for Uruguay, Luis Suarez, it looks the toughest examination so far of an Inter season in which Conte has so far overseen six wins out of six in Serie A, the one poor result the 1-1 draw in Milan that began Inter’s European campaign.
After that result, and with Borussia Dortmund also in a group where all four teams have one point, Inter and Barca cannot easily make Wednesday night one of those autumn Champions League fixtures where heavyweights nod cautiously at one another, settle for a draw and wait until December to sort out who finishes top and who second.
Yes, there will be respect, above all between Godin and Griezmann, but friendly gestures are on hold until afterwards.
