The question: Are the 35-year-old Federer's backhand, quads and calves so impervious to the ravages of time that he can stand on or inside the baseline and crunch winners against anyone? Or is injury-plagued, 29-year-old Nadal still simply not the same player who ran up a 23-9 record against Federer before their three most recent meetings?
No buzzkill intended, folks. Only a misanthrope would have failed to go a little giddy at the sight of Federer slashing and lashing away Wednesday night, slicing Nadal to pieces small enough to fit into a two-set box. But the reality remains: Nadal may be on the way back, but in the big picture, he is still on the way out.
Nick Kyrgios will have his chance to weigh in on whether the lopsided fourth-round result was more about Federer's ageless abilities or Nadal's decline when the talented Aussie meets the rejuvenated Swiss superstar in Friday's quarterfinals on ESPN2 and the ESPN App.
Kyrgios is both explosive like Stan Wawrinka and extremely quick like Djokovic. Unlike Nadal, Kyrgios hits a relatively flat ball that will make it harder for Federer to set up shop on the baseline. Unlike Raonic, who clubbed Federer into the turf in the Wimbledon semis last year, Kyrgios is also inventive, capable of changing the pace and tone of rallies. A lean and sinewy 6-foot-4, Kyrgios also has greater agility than Raonic.
But the most lethal arrow in Kyrgios' quiver is his serve -- the one that allowed Djokovic no break points in their meeting Wednesday. The one that hit 140-plus mph and averaged up in the 120 mph range on second deliveries. The one that produced 14 aces. That's better than one per game. Unreturnable serves may not be as sexy, but they count the same as an ace, and Kyrgios hit a boatload of those, too. All that against the man generally acknowledged as the best returner in the game.
So Federer will be up against a man who can shut him down before he gets started, something Nadal, who never met a 40-shot rally he didn't like, is neither designed nor inclined to achieve. What's Federer to do?
First off, Federer can trust his game, which should come easily to an 18-time Grand Slam champion hailed widely as the greatest player of all time. He's still breathing the ambrosia of that win at the Australian Open, as well as his three straight wins over Nadal.
Federer's confidence is zooming. He's playing bold, aggressive tennis. On Wednesday, he told Tennis Channel commentators: "I have easier power, and I gained confidence [with the 98-inch Wilson racket]. And once you have the confidence, you step in, and once you step in, then it's easier to pull back again."
Federer can also rely on his deep well of experience, especially if the match is close or controversy looms. Kyrgios' emotional drop-down menu includes tabs for meltdowns and letdowns. But those options may be disappearing. The expressive Aussie seems to have learned the value of anger management, a useful tool if the Palm Springs swells start oohing-and-aahing over Federer and his lustrous hair and great backhand.
Letdowns are another matter. Kyrgios has struggled with them. In Acapulco a few weeks ago, he was unable to back up his quarterfinal upset of Djokovic and lost to Sam Querrey in the next round. Granted, Querrey was on fire all week, but it was another reminder that the most difficult task once an upset is registered is following it up with a win -- no matter who the opponent.
"It's just another match for me," Kyrgios said in his presser. "I have to get ready for tomorrow. I am serving really well -- that is creating chances for me to put pressure on their service games. My mentality is improving, and I am trying really hard to fight for every point and just compete."
Federer did great damage against Nadal with the one-handed backhand that, throughout their rivalry, had been seen as the main source of Federer's dispiriting head-to-head deficit. That history was one reason so many fans went ga-ga over Federer's performance. It seemed to confirm that miracles can still happen. That genius will always find a way.
"By coming over my backhand on the return, from the get-go of the point, I can dominate points right away," Federer said. "It's important to keep your opponent off-guard and know that he has to be careful."
All true. But the imminent problem for Federer is that there is zero commonality, at any level, between his last match and this next one. Nadal has a serviceable lefty serve. Kyrgios' serve reminds us of ancient pitcher Walter Johnson's famous line, "You can't hit what you can't see."
Kyrgios has the ability to make the Federer-Nadal match look like a happy stroll down memory lane, ending with a thud at the gate to the future. And if not, so much the better. The world can't seem to get enough of Federer -- nor he of the world.
Does anyone really care if the chicken or egg came first anyway?