Federer and Nadal saw their rivalry peak at Wimbledon, 2008.
Is this the greatest rivalry of all time?
Tennis has produced great individual stars and revolutionary technology changes since the advent of the Open Era in 1968. What makes some rivalries timeless while others are soon forgotten? Here are five criteria to measure a rivalry:
1) Grand Slam Battles: Rivals must compete on the biggest stages of tennis, preferably often. High stakes are needed to provide a forum of pressure and measure champions.
2) Fan Interest: Passionate fan bases and writers want compelling stories.
3) Player Personalities: Usually a clash or contrast of personalities provides greater theater. Sometimes both personalities are favorites, but sometimes one player will play the villain. Rarely will two bland personalities capture as much attention.
4) Contrast of Styles: A classic example pits a baseline tactician vs. a serve-and-volley expert. With changing times, new hybrids of style are emerging.
5) Big Moments: Tennis fans can often recall exact moments in great matches. It is the essential ingredient for immortality.
Ready? Let's begin the countdown.
Clijsters and Henin was magnificent tennis, but overlooked.
Not all great rivalries crack the top ten, but some are deserving of a line or two:
Jim Courier vs. Stefan Edberg (1991-1993)
Their styles transitioned two eras, until Sampras took over.
Roger Federer vs. Novak Djokovic (2008-present)
Federer got the upper hand in a few good clashes, but only one Slam final.
Margaret Court vs. Billie Jean King (1963-1970)
Strangely, both remembered more for their matches against Bobby Riggs.
Justine Henin vs. Kim Clijsters (2003-2004)
The crown jewels of Belgian tennis were amazing athletes and underrated champions. Too bad the American hype machine never seemed to notice.
Mats Wilander vs. Ivan Lendl (1983-1988)
Combined for 15 Grand Slams, but never established great personal rivalries or moments.
Venus and Serena didn't smile much during their matches together.
In sports, a tie is like kissing your sister, because of its unsatisfying result. Unfortunately, this is a more apt description of when the Williams sisters opposed each other.
The hype preceding the matches was rarely matched by their play on the court. Their similar styles and aggressive natures produced error-filled tennis, and usually lopsided results. Only twice in eight matches did they duel to a third set.
It was more interesting to watch the Williams sisters battle Martina Hingis, but in the end were part of what drove Hingis from tennis.
There was always a sense of mournfulness and tension watching the Williams sisters, and then much of the tennis world just didn't care anymore.
Rocket Rod Laver had an aggressive all-court game, and a variety of shots. Like Federer, he had so many weapons he could sometimes get caught in deciding between strategies. His legacy was immortalized when twice winning the calendar Grand Slams.
Ken Rosewall's weapon was a trademark slice backhand. A fast, agile athlete, he hustled for eight Grand Slam titles, including a split of the two French Open Finals clashes with Laver.
The rivalry would be higher with more Grand Slam Finals together, and with some modern media hype.
Boom Boom Boris Becker's powerful serve and volley game produced memorable highlight lunges and dives. The fiery German athlete excited young Generation X tennis players by capturing two Wimbledon titles by age 18.
Stefan Edberg's grace and touch at the net are perhaps the finest fundamentals ever displayed. He seemed to always find the right spot to angle a deft volley.The Swede's coolness also prevailed in two of three straight Wimbledon contests against his more charismatic rival.
Nadal defeated Djokovic in their first Grand Slam meeting.
The beauty of this rivalry is their relentless intensity. Currently, Rafael Nadal's gamely spirit has not been enough to break Novak Djokovic's upstart dominance.
Fortunately, the 2012 Australian Open provided one of the most epic matches in tennis history, adding more intrigue to future clashes.
The upcoming French Open could be Nadal's chance to regain a piece of the throne. Or Djokovic could vanquish his Spaniard rival and rule tennis with an iron fist.
They were two fiery left-handers who acted out their raw emotions on Centre Court for the whole world. New Yorkers love it. Wimbledon's press was horrified.
McEnroe's genius was serve and placement and an artist's touch. It was surpassed only by his perpetual scowl.
Connors' aggressive baseline play was often celebrated with fist-pumping. He could take an entire stadium and turn it into a house of horrors for opponents.
Too bad they only met in two Wimbledon Finals, but great fireworks is not meant to last.
It's not possible to discuss their rivalry without wondering "what if?" Before Seles was tragically stabbed in 1993, she had taken control of women's tennis with her frying-pan laser shots.
Steffi Graf, with her brilliant slice backhand and big forehand, would continue on and solidify her legacy as the greatest player in women's tennis, dominating on every surface.
Seles resumed her comeback in 1995, but she had lost her steely confidence and was a step slower.
Maybe Agassi should have worn his pirate outfit a few more times against Sampras.
Pete Sampras announced his arrival to tennis greatness by crushing crowd-favorite Andre Agassi in the 1990 U.S. Open Finals. It would prove prophetic.
Theirs was an on-and-off rivalry relationship, noteworthy only when Agassi was fit and motivated. Agassi's image was captured a thousand different ways, but he still provided fabulous tennis moments and beautiful ground strokes.
Pistol Pete was often viewed as Agassi's boring counterpoint, but ultimately the greater tennis player. He was at his best when called upon to beat down the Agassi hype, which he did four of five times in Grand Slam finals. Sampras also had a penchant for knocking back his other American counterparts, Jim Courier and Michael Chang.
How differently we would have viewed their rivalry had Agassi won a couple more of their Grand Slam clashes. But Sampras rode off into the sunset by winning his final Grand Slam against...Andre Agassi.
The American public clearly loved and rooted for Chris Evert and her baseline game, but it was Navratilova who most often dominated with her serve and volley. She won ten of their fourteen meetings in Grand Slam finals.
Suppose both players began their careers in the '90s: Evert's game might have been more enhanced with technology to add more punishing speed and spin to her ground strokes.
The familiar saga of Nadal's dominance over Federer continues.
From 2005-2008, Nadal alone held back Federer's world conquest, defending the red clay at Roland Garros as if it were the last piece of territory on Earth.
Their rivalry peaked at Wimbledon, 2007-2008, splitting two titanic five-setters and inspiring L. Jon Wertheim's vivid book, Strokes of Genius.
Federer, for all his accolades as the greatest player of all time, never could solve Nadal's heavy topspin and angled passing shots.
It's still too early to completely archive their accomplishments. There could be one last immortal clash.
Borg's cool mystique and all-court brilliance made him the Federer of his time. McEnroe's feisty resistance and swashbuckling manners created the ideal bad boy.
Both titans collided at the peak of their powers. Each could defeat the other and fascinate the tennis world. The only sadness to their rivalry was Borg's abrupt retirement at age 26, when he still was arguably at his peak.
Borg vs. McEnroe is timeless. Each July, we see them at Wimbledon as the standard of rivalries. Their legend has been enhanced, not diminished, by the passing of decades. We don't know if Nadal vs. Federer will have this same status.