For the most part of two decades, people around the world have been tuning in to watch veritable sports giants Serena Williams and Roger Federer battle against their opponents in order to fight their way to victory. Tomorrow, however, only one of them will win their game - as they'll be playing against one another.
In a hotly-anticipated match, the two superstars will go face-to-face at the Hopman Cup in Perth, Australia, in order to determine who the world number one really is as part of a mixed-doubles match with their partners Belinda Bencic and Frances Tiafoe.
"It's very exciting for both of us," Federer told the Australian Associated Press.
"I hope a lot of tennis fans will tune in to watch the match, because it's going to be one time and probably never again in this kind of a competition."
Unlike other sporting opponents, both Federer and Williams seemed to actually have some rather nice things to say about one another.
"I admire everything [Williams has] done on and off the court. We can relate to one another now even more so for being parents," the Swiss player said of his opponent.
"I've played with some of the greatest doubles players in the world in Martina Navratilova and Martina Hingis, and I've also played against some of the best in Venus [Williams] and other great ones in the past.
"This time it's against Serena, who is one of the biggest champions ever in our sport - men and women combined."
Meanwhile, Williams said that the opportunity to play Federer was "like a dream come true", adding: "I have been looking forward to it. This is so cool."
Though it is unusual to see such esteemed male and female champions go head-to-head in tennis, it is not totally unprecedented. Back in 1973, the 'Battle of the Sexes' saw 39-time Grand Slam champion Billie Jean King take on former men's world number one Bobby Riggs. King ended up thrashing her opponent in straight sets - despite what many pundits expected.
As the event is mixed doubles, however, the two players will be counting on their partners to put in a good game, too.
According to the BBC, "The Hopman Cup comprises two singles and a mixed doubles match between nations in a round-robin format with two groups of four. The winners of each group will contest Saturday's final."
So far, Federer and his partner have won their opening match, but Williams and Tiafoe weren't so lucky. Still, the American champ did win her singles match, so she's proven that she's fighting fit for the tournament.
Team Switzerland are actually the defending champions of the Hopman Cup, as Federer and Bencic won the event at the beginning of this year. Whether or not they've got what it takes to do it again remains to be seen - but, right now, the odds are certainly in their favour.
As far as sport in 2019 goes, then, this is sure to be a good start!
