Novak Djokovic and Roger Federer faced off in the Cincinnati final last month.
The rivals will stand shoulder-to-shoulder as partners in Chicago tomorrow night.
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The second-ranked Federer and third-ranked Djokovic will partner in doubles on opening night at the Laver Cup.
The pair, who have combined to win 34 Grand Slam singles titles, lead Team Europe against the Team World pairing of Jack Sock and Kevin Anderson.
The Friday night session begins with David Goffin (Team Europe) playing Diego Schwartzman (Team World) at 7 p.m. before the blockbuster doubles.
The 20-time Grand Slam champion said he's intrigued to see what kind of dynamic Djokovic will bring because "I don't know him that well."
"With Novak, it's different because I know him well, but I don't know him that well," Federer told The Chicago Tribune's Amy Carr. "With him, I'm very excited to see how the week's going to go because I don't think both of us know really, really what we think of each other. I don't know what kind of a team leader he will be on a team.
"With Rafa, I have done so many promotional events around tournaments. I've done foundation matches with him, and I know his family very well. So I feel like I'm much closer to Rafa. And, also (Andy) Murray, I did a foundation event with him and a lot of other top guys. Novak is one of the only guys I haven't done it with. So that's going to be interesting just to see the dynamics there."
Last year, Federer and Rafael Nadal partnered in doubles.
Team Europe captain Bjorn Borg surprised World captain and long-time rival John McEnroe pairing Djokovic and Federer on opening night.
"I did have an inkling they would play," McEnroe said. "I am surprised they would play the first day."
In the aftermath of his run to his 14th Grand Slam title at the US Open, Djokovic said Federer and Nadal have inspired him to elevate his game.
"I have utmost respect for what they have achieved on the court, but also the champions, role models they are off the court," Djokovic said. "I think we have pushed each other to the limit every time we get to play each other. For me, that was always an ultimate challenge: to play Nadal or Federer anywhere.
"I think, you know, I had to figure out early in my career, when I was losing most of the big matches on the Grand Slams against them, what it takes for me to actually kind of improve and develop my game to be able to challenge them, to be able to start winning against them when it matters the most. I think that was one of the most important, so to say, moments and periods of my life, my tennis career, my development. I owe it to them."
Laver Cup begins at 1 p.m. on Friday with Grigor Dimitrov (Team Europe) meeting Team World's Frances Tiafoe.
They will be followed by Laver Cup debutant Kyle Edmund (Team Europe) against Jack Sock for the World side.
Photo credit: Laver Cup Facebook