There was a time when a Grand Slam final between Roger Federer and Rafael Nadal was a regular occurrence.
Over a 12-major span from the 2006 French Open to the 2009 Australian Open, seven title matches were Roger vs. Rafa. No other pair of men in tennis history participated in a total of more than six Slam finals together.
"A lot of important matches for our careers," Nadal said. "A lot of emotions in these kind of matches."
And then, suddenly, it stopped. Federer and Nadal will renew their sublime rivalry Sunday at the French Open, the first time in more than two years they'll decide a Grand Slam championship.
As usual when it comes to Federer and Nadal, there is plenty at stake.
The top-seeded Nadal is 44-1 at Roland Garros and bidding for his sixth French Open championship, which would equal Bjorn Borg's record. Only two days after turning 25, he'll be going for a 10th major title overall. Plus, he needs a victory to prevent Novak Djokovic from replacing him at No. 1 in the ATP ranking.
The third-seeded Federer, meanwhile, seeks to add to his record of 16 Grand Slam trophies, including the 2009 French Open. He could become only the third man to own at least two titles from each of the sport's most important tournaments (he's won six at Wimbledon, five at the U.S. Open, four at the Australian Open).
And then there's this intriguing tidbit: Federer never has beaten Nadal at Roland Garros, going 0-4 - in the 2005 semifinals, and the 2006, 2007 and 2008 finals.
The only time Federer managed to win the French Open, he didn't have to face Nadal. Instead, Federer's straight-set victory in the 2009 final came against Robin Soderling, who stunned Nadal in the fourth round that year (and also happened to knock out Federer in the 2010 quarterfinals).
"It always seems to me that Rafa needs to be in a French Open final to make it special," Federer said after ending Djokovic's 43-match winning streak in the semifinals, "and I got the match I guess I was hoping for."
That's a fascinating statement, considering that Nadal is a player who troubles Federer in ways that no one else ever has. Nadal is 16-8 against Federer overall, including 5-2 in Grand Slam finals. Nadal won their most recent match, on clay in Madrid last month.
In the semifinals against Djokovic, Federer served spectacularly, and he displayed all of the strokes and mental toughness that led many to consider him the greatest tennis player ever.
As 1999 French Open champion Andre Agassi put it Saturday: "I do think that the way Federer played yesterday, he can beat anybody in the world - and probably anybody in the future."
And then Agassi added: "But there's something that he brings out in Nadal."
One part of Nadal's game that's consistently bothered Federer is his heavy-topspin, high-bouncing, left-handed forehand - which can arrive at about shoulder-height on Federer's backhand side.
Nadal also tends to have remarkable success at staving off break points against Federer.
These two players know the ins and outs of each other's games well, and many of their matches have been tight. Three of their past four head-to-head Grand Slam finals went five sets.
The exception, though, was as lopsided as could be: The last time they played at the French Open, in the 2008 final, Nadal won 6-1, 6-3, 6-0.
Given how Federer played against Djokovic, the expectation is that Sunday's final will be competitive - and perhaps much, much more than that.
"It will be one for the ages," Agassi predicted. "Any time you see these two, Nadal and Federer, it's one of the most memorable moments. We've been spoiled. It's an incredible rivalry and I think we'll look back on this as probably one of the best our sport's ever had."