Last November, Roger Federer hopped on a short flight to Manacor to help Rafael Nadal open his new academy and the pair shared a joke about how their respective injuries left them unable to even have a celebratory hit.
Ten months on and both men have two more Grand Slam titles under their belts. Unless something truly remarkable happens over the next couple of months, one of them will end up as the world No.1 for the year while the other one is No 2.
It has been an incredible year, with Federer winning in Australia and at Wimbledon, where he won the title for an eighth time, and Nadal adding the US Open title to his 10th French Open crown.
Nadal is in the driving seat when it comes to No.1, with a lead of almost 2,000 points, but he knows there is still a lot to play for in the remaining two months of the season.
“Well done for Roger that he is having an amazing season too and well done for me because I'm having a great season too,” Nadal said after his win over Kevin Anderson, a third US Open title that lifted his Grand Slam tally to 16, three behind Federer - the same as it was all those months ago in Manacor.
Indeed, for all his stunning exploits this year, Federer has been unable to pull away from Nadal's Grand Slam count, and with the Spaniard five years his junior, one wonders if he may yet end up with the most major titles to his name.
It's a debate that fascinates fans and analysts alike, but less so Nadal himself.
"I don’t think about if Federer won two tournaments or four or 24," he said after his US Open triumph.
"I follow my path, and what motivates me is my career, not the career of others. Let's see what happens until the (end of the) season and that's it. Tennis is not all (about) the grand slams, so there are tournaments to come and I'm excited about this last part of the season.”
So, too is Federer, who usually comes into his own when there is a roof over the court and who will be itching to get back at it, having lost to Juan Martin del Potro in the quarter-finals, perhaps not 100 percent fit after struggling with a sore back in the build-up to the US Open.
With Masters 1000s in Shanghai and Paris, followed by the Nitto ATP World Tour Finals, where 1500 points are on offer to anyone winning all five of their matches, a lot may yet change between the two.
I follow my path, and what motivates me is my career, not the career of others
“I hope I'm going to arrive really early in Shanghai to really get ready and make it a priority for me to win that tournament,” Federer said in New York.
“I'll be fine even without No.1. I have had a great year thus far. I have big priorities for the rest of the year, and I usually play very well towards the end. Now I just really need to recover and go back to the practice courts and hopefully just finish strong. Whatever that may be, I just want to play good tennis and enjoy myself.”
Though Federer and Nadal have won the four Grand Slams between them on several occasions, it is the first year ever that they have split them evenly.
Repeating what they did this year again in 2018, however, may be even more difficult than what they have achieved in the past nine months.
Such is the emphasis on physical strength these days on the Tour, over the past five years, no one has really managed to dominate in two straight years.
And with Andy Murray, Novak Djokovic and Stan Wawrinka all hoping to bounce back from injury lay-offs – just as Federer and Nadal did in 2017 – things may change again, especially with Federer now 36 and Nadal 31.
I'll be fine even without No.1. I have had a great year thus far
Carlos Moya, the coach of Nadal, said the next step for his man will be beating Federer again, having lost to him in the Melbourne final, and then again in Indian Wells and Miami.
“In Miami we tried to change a few things, but it didn’t work,” Moya told a group of reporters. “It’s about evolving. When you lose two, three, four times to the same guy, you try to find something.”
Pat Cash, the former Wimbledon champion, told BBC Radio 5 Live in New York that Federer is more likely to dominate than Nadal in 2019.
“Take away the French Open and Federer is the best all-round player in the world," he said. "There's no doubt about that. He's my favourite for everything apart from the French.
"As long as he's fit, he's favourite for the Australian, Wimbledon and the US Open."
Either way, the last couple of the months of the season will decide who ends up on top, for now, at least.