Both of them were injured — Federer was recovering from knee surgery, Nadal had an ailing wrist. And neither knew when they'd return to top form and perhaps contend for Grand Slam titles again.
It turns out the wait wasn't long. Federer beat Stan Wawrinka on Thursday to reach his first Australian Open final since 2010, and Nadal could join him with a victory in his semifinal match with Grigor Dimitrov on Friday.
"I was on one leg. He had the wrist injury. And we were playing some mini-tennis with some juniors and we're like, 'This is the best we can do right now,'" the 35-year-old Federer said of their time together in Mallorca.
"We would have never thought that we were going to be here, potentially playing in a final."
Few people would have given either player much of a chance to get this far.
Federer's 2016 season was marred by an injury he sustained following the Australian Open when he twisted his knee while drawing a bath for one of his four children. He returned swiftly after surgery, but fell on the knee during his semifinal loss at Wimbledon and was sidelined the rest of the year.
Coming into this year's Australian Open with a low seeding of 17th, Federer didn't expect he'd win more than a few rounds. Particularly when he saw a draw that included potential match-ups with top-10 players Tomas Berdych, Kei Nishikori, Andy Murray and Stan Wawrinka.
But the 17-time major winner swept past Berdych and Nishikori, and Murray was upset by Mischa Zverev.
Then, with the crowd urging him on against Wawrinka, Federer fended off two break points in the pivotal fifth set to beat his countryman 7-5, 6-3, 1-6, 4-6, 6-3 and reach the 29th major final of his career.
Suddenly, the aging veteran hobbling around "on one leg" has a chance to capture Grand Slam title No. 18.
And he's winning energy-sapping, lengthy matches, too. With his five-set wins over Nishikori and Wawrinka, it's the first time since the 2009 French Open that Federer has won two five-setters in the same tournament.
"I'll leave it all out here in Australia and if I can't walk for another five months, that's OK," he said.
Federer looks back on his six-month injury layoff now as a positive step to returning fully healthy and ready to compete with the top players again.
"What I've just come to realize is when you don't feel well, you have too many problems going on, you just won't beat top-10 players," he said. "You can play them tight. You might win one of them. You just can't win back-to-back."
Nadal has realized this, as well. He also took two extended breaks last year to let his wrist heal properly — and looks fresher here in Melbourne. He's back in a Grand Slam semifinal for the first time since he won the last of his 14 majors at the 2014 French Open.
"Of course, it would be unreal to play (Nadal) here," Federer said. "I think it's very special for both of us, this tournament, already."