When Roger Federer filmed a question-and-answer session on the eve of Wimbledon, he was asked: "Who's the player you dread playing the most?" and: "Who's your favourite player to play against?"
Federer said the same thing both times: "Rafa Nadal."
The answer was revealing, even down to the preference for "Rafa" over the more formal "Rafael". Federer and Nadal may have their inevitable differences and mini-grudges, but they also understand the value of a great rivalry. Even if they have cost each other dozens of titles, they will be more fondly remembered as a result.
Yet if you strapped Federer to a camp bed and applied a shot of truth serum, would he give the same answer? One suspects not. Surely the match-up he really fears is the one he faces on Sunday. Surely his true nemesis is not Nadal, but the ultimate tennis wall: four-time Wimbledon champion Novak Djokovic.
Yes, Nadal might have dominated Federer in the early part of this decade, winning nine straight sets at one stage. But that dynamic has changed completely, as we were reminded on Friday in a memorable semi-final.
At the start of 2017, Federer came back from his six-month sabbatical with an upgraded backhand and a new, clear game plan for beating Nadal. He has yet to figure out the same for Djokovic, who is apparently uncrackable: tennis's equivalent of the Enigma machine.
The head-to-head scoreline stands at 25-22 in Djokovic's favour, which is worrying enough in itself. But when you knock off the early skirmishes and count back to the Australian Open of 2011 - the moment when Djokovic discovered his superpowers like some character from the Marvel universe - the disparity becomes much greater: 20-9. Worst of all, Federer has not won over the best of five sets since the Wimbledon semi-final of 2012.
Federer and Nadal give every impression of revelling in their ice-and-fire narrative, as John McEnroe did in his pursuit of Bjorn Borg. Even Martina Navratilova and Chris Evert, who had their tetchy moments, came to appreciate each other by the end.
With Djokovic, though, it feels like both older men see him as an irritation. He is the gooseberry in their great tennis romance, or perhaps the scrappy younger brother, whose nuisance value is only enhanced by the fact that he threatens to bypass them both on the overall grand slam standings.
Even when it comes to tennis's backstage wranglings - which have been more toxic in recent months than anyone can remember - the tensions and alliances remain polarised.
Djokovic is not just the world No 1 but the most influential player behind the scenes, and in March he catalysed a coup against Association of Tennis Professionals chief executive Chris Kermode. The next day, Federer expressed his disapproval to Tennis Channel interviewer Jon Wertheim.
"I think everything [in tennis] is going great and then you talk about politics and you're like, 'Oh my God, what's going on here?' " Federer said, in an unusual departure from his customary Swiss neutrality.
"I spoke to Rafa the other day for quite some time, he came to the house and we had coffee together, and we just were really going through what is going on. I'm happy that we're aligned and we agree that we should be talking and coming up with a proper plan." The "proper plan" has yet to materialise, but the comment was another glimpse into the respective mindsets of the Big Three. On a personal level, it is hard to see Djokovic showing up to the Federer mansion for coffee.
Even now, four months on, the two men have yet to discuss the many awkward issues bubbling away in the background.
In tennis politics, as in the day-to-day business of forehands and backhands, Djokovic is the prime mover of the men's tour: the guy who gets what he wants. He has been the world's best player for the last eight years, with the exception of a two-year stretch when he went off the boil after the 2016 French Open.
That interregnum was a rare moment of vulnerability. Having pulled off the almost impossible feat of holding all four majors simultaneously, Djokovic lost his appetite for the game, while also suffering a chronic elbow injury which required him to undergo surgery for the first time in his career.
But since emerging from his slump at last summer's Wimbledon, normal service has been resumed. At the grand slam tournaments - the only events which really motivate him these days - he has won 32 of his past 33 matches. The only exception came against clay-court maestro Dominic Thiem in gale-force winds at last month's French Open.
So how can Federer overcome those odds, and thus defeat both his leading rivals at the same slam for the first time? It might seem an almost impossible challenge for a 37-year-old, but the years seemed to drop away during Friday's semi-final, as he gambolled across the Centre Court turf like a young deer.
Is there any tactic that could upset Djokovic, the man with all the answers? Lights-out serving can hurt anyone, even the greatest returner that the game has seen. And then there is the knifed backhand slice, played up the line to the Djokovic forehand. He does not enjoy having to generate his own pace off that wing.
But these are minor blemishes. As Djokovic said on Friday, having comfortably overcome Roberto Bautista Agut in a four-set semi-final: "I believe I have what is required to win on this surface. I am not worried whoever is across the net." He has earned the right to consider himself the new king of Centre Court.
That same evening, Federer's children sang "Happy Birthday", having seen dozens of people congratulating him and jumped to the wrong conclusion. "Perhaps that is the only happy song they know," he explained with a grin.
Could there be a repeat performance on Sunday night? If he wants another serenade, Federer will need to play one of the best matches - maybe THE best - of his long and glorious career.