Australia Tennis ATP Cup
They're the only two players to have clashed in all four grand slam finals and now tennis titans Rafael Nadal and Novak Djokovic will collide for the first - and possibly only - time in Sydney after setting up the ultimate climax to the ATP Cup.
Nadal broke Australian hearts with an iron-willed comeback win over Alex de Minaur to lead Spain to victory in Saturday night's second semi-final after Djokovic helped Serbia to a 3-0 win over Russia.
Now the world's top two players will bring the sport's most abiding rivalry to Sydney on Sunday night in a dream sequel to last year's Australian Open final - and possibly a preview of the 2020 decider as well.
Their latest showdown will be a record 55th instalment in their career-long rivalry.
Nadal's 4-6 7-5 6-1 fightback against de Minaur came after 2019 Wimbledon semi-finalist Roberto Bautista Agut burst Nick Kyrgios's bubble with a 6-1 6-4 win to put Spain 1-0 up.
Djokovic earlier breathed a huge sigh of relief after pulling out all stops to deny Daniil Medvedev and clinch victory for Serbia with a 6-1 5-7 6-4 triumph over the world No.5.
Dusan Lajovic had upset world No.17 Karen Khachanov 7-5 7-6 (7-1) in Saturday's opening singles rubber at Ken Rosewall Arena to give Serbia the early initiative.
Runner-up to Nadal at last year's US Open and unbeaten in his four singles rubbers this week, Medvedev threw everything at Djokovic.
He had the world No.2 repeatedly doubling over and gasping for air after a series of long-busting baseline duels.
But, not for the first time in his distinguished career, Djokovic had the answer, the 16-time grand slam champion breaking the Russian for a fifth time in the fifth game of the deciding set and finally prevailing on his second match point, after saving three break points of his own in the very last game.
"It was very exhausting," a mightily relieved Djokovic said, having obliterated a racquet during a second-set tantrum while trying to find a way through the Russian's defences.
"It was a big battle all the way to the last shot. Daniil Medvedev is one of the best players in the world and, today, he showed why.
"It seems he's a machine."
Djokovic hasn't played a pre-Australian Open tournament down under in a decade, preferring to spend his summer trying to peak for the season-opening major that he has won a record seven times.
But the 32-year-old said he made an exception this year for the honour of representing his country.
"I love playing for Serbia and for my country, and team competitions is something that gets me going tremendously," he said.
But the gruelling workload of five singles and one doubles match over the past seven days - plus at least one more in Sunday night's final - has forced Djokovic out of next week's revamped Adelaide International.
"I was hoping there was going to be this many matches and this much intensity, because that means we would do well," he said.
"I did sign in for Adelaide because I didn't know how ATP Cup is going to go for us.
"So you could have also finished it pretty early after group stages, and you want to have more matches coming into Melbourne.
"We got so far here that I just need to conserve energy after this competition is done for Melbourne."