The French Open has often been a reminder of Grand Slam heartache for Roger Federer, but every great player has matches he wishes would have been reversed.
The most painful losses are often the matches that great players recognize as a lost opportunity to make history, to extend their dominance, or dispatch a rival.
This article will feature the most important (usually most regretful) loss in the careers of ten tennis legends. Each player is only allowed to reverse one match.
Oftentimes, a great rivalry match can have a ripple effect on future matches and tennis history. This countdown will attempt to rank the importance of each match, and how it could have altered history.
Djokovic was riding a 43-match winning streak into the 2011 French Open semifinals, but Federer's convincing 7-6, 6-3, 3-6, 7-6 win ruined Djokovic's opportunity to play Rafael Nadal in the finals.
This was an important match that could possibly grow in magnitude should Djokovic fail to capture a French Open title.
Had Djokovic carried his momentum and success against Nadal into the 2011 French Open final, he might have already completed his Novak Slam by the the dramatic 2012 Aussie Open. Maybe he rides this to thorough tennis domination for the next few years.
But in 2012, the worm has turned. Nadal has seemingly regained his upper hand on clay versus Djokovic, and the pressure may continue to mount on the young Serb to win the French Open now or within the next few years.
On the other hand, if Djokovic had defeated Federer and lost to Nadal in the 2011 final, maybe it's the Spaniard who would ride this victory to turning things around at the next three majors.
The implications and possibilities are still being sorted out, but it was a crucial loss for Djokovic.
In 1978, Connors was whitewashed by Borg's 6-2, 6-2, 6-3 thrashing that would prove to be the third of five titles in a row for Borg at Wimbledon.
Though Connors had narrowly lost a 5-setter to Borg at Wimbledon in 1977, his crushing defeat in 1978 was the last time he made it to the Wimbledon final until Borg's abrupt retirement.
He did turn the tables on Borg a couple months later at the U.S. Open to keep the chains on his career moving, and eventually had a renaissance in 1982-1983 with three more Grand Slam titles, but only after Borg was out of the picture.
A win for Connors would have interrupted Borg's now legendary five consecutive Wimbledon titles. It also might have shattered some of the mystique and dominance Borg had, and perhaps Connors would have eventually been recognized as the better player.
Interestingly, this is a similar parallel facing Nadal. If he goes on and wins a few more French Open titles but is not able to capture more Slams on other surfaces, critics may ultimately place him behind Federer and Djokovic.
1984 was McEnroe's chance to play Big Brother in a historic year that saw him go 82-3 with easy straight-set victories at Wimbledon and the U.S. Open.
But he will forever rue the French Open where he was up two sets and a break before melting to Ivan Lendl.
He referred to the match in his autobiography as a bitter defeat, and he would never again come close to winning the French Open.
Besides being the fly in the ointment of a nearly flawless year, this loss seemed to foreshadow McEnroe's tailspin that would begin in 1985. Perhaps his dominance would have continued had he won the French Open.
It also opened the door for Ivan Lendl in turning his career around. Lendl would have eventually got his Slam titles, but maybe McEnroe would have had nine or 10 Slams to Lendl's five instead of trailing 8-7 in their all-time totals.
Nadal does not have a single career-wrecking match, but there are a handful of matches the Spaniard wishes he could have reversed. Sure, it would have been nice to have won the 2007 Wimbledon classic, but he redeemed himself in 2008 and 2010, and continued his upper hand on Federer.
Though the 2010 Australian Open title would have given him a Rafa Slam, defeating Ferrer would not have likely led to a title with his bad knees.
The 2012 Australian Open was a tough loss that will forever haunt him, but it now appears that Nadal can overcome its effects and charge forward in the coming months and years.
Had Nadal won his third Wimbledon and third French-Wimbledon double, it would have provided complete mastery over a second surface, further dominance on the tour, and perhaps held back Djokovic the next two Slams as well.
We could be talking about 12-13 Slams and counting, and of a clear-cut status as the dominant player in both rivalries with the other big two.
Third-seeded Edberg had just defeated Boris Becker in a tough five-set semifinal, which partly contributed to losing his 2-1 sets lead against No. 15 seed Michael Chang.
He probably still wonders how he lost that match, the closest he would ever get to winning the French Open, and the only Slam that would elude him.
Once again, another great serve-and-volley artist would die on the red clay, and to this day the impossibility of this style winning the French Open is reinforced. If only Edberg had held on.
For Michael Chang, this would be his life's greatest work and one of the great tall tales in tennis history, from his endurance victory in the fourth round versus Ivan Lendl to the championship win versus Edberg.
It perhaps drove Chang to his maniacal obsession to win another, and invest the rest of his career to come close again, but he'd never win another. He will always have the French Open and a place in tennis lore.
Edberg, one of the purest artists in tennis history, missed his chance for a career Grand Slam and perhaps a spot ahead of McEnroe, Lendl, and Becker. A victory at the French Open would have given him sole serve-and-volley status amongst all-time tennis legends in succeeding on slow clay.
Another agonizing 1980s story was Lendl's eternal quest to capture tennis's Holy Grail, the Wimbledon title.
In 1986, Lendl's great season, complete with French and U.S. Open titles, was marred only by his defeat to popular young Boris Becker.
Lendl would also lose a year later to Pat Cash in the Wimbledon final, which was a surprise to mainstream tennis fans, but in retrospect not much of an upset to the gritty serve-and-volley Aussie.
Had Lendl won his obsession, he would have had his career Grand Slam and perhaps raised himself into the all-time top five pantheon. He would have garnered great respect in knocking back Boris Becker, and perhaps gained greater popularity amongst tennis fans.
Though Andre Agassi eventually proved a baseline game could win on the fast lawns at Wimbledon, Lendl could have done it earlier and perhaps interrupted Becker, Edberg, and Cash for a second or third.
In 1996, Sampras had overcome a two-set deficit to defeat Jim Courier in the quarterfinals.
Unfortunately, he had to run into Kafelnikov and his brilliant backhand. Kafelnikov was a buzzsaw, ripping through all but one match in straight sets, and seemed destined to be a dominant player.
Had Sampras won this match, there is no question he would have defeated Michael Stich in the final, a player who was a poor man's Sampras, but was aging and had somehow made a last surprising run.
This would be Sampras's only legitimate chance at winning the French Open, and denied him greater historical claim to being supported as the Greatest of All-Time (GOAT).
Federer fans are thankful that Kafelnikov did his damage in order to give their man greater claim to the GOAT label, though Sampras fans can justifiably still find their claims to this debate.
Borg's classic victory over McEnroe in the 1980 Wimbledon final has been immortalized, but the two dueled again in another five-set match at the U.S. Open, with McEnroe prevailing this time 7-6, 6-1, 6-7, 5-7, 6-4.
Borg's heartbreak saga at the U.S. Open was punctuated with this loss. He did not serve well, but rallied to force a fifth set, before ultimately fell short.
Borg would lose both matches a year later to McEnroe at these venues and then run off into retirement.
If Borg had won another close match against McEnroe, perhaps he would have held his mental edge another year or two. It was getting harder as he also needed five sets to prevail against Lendl in the 1981 French Open, but the leaking of his dominance can be traced here.
Maybe a Borg victory would have deterred McEnroe, and Connors would not have come back with his 1982 success.
Most tennis fans wish Borg would have played another five years, but by 1991 when he did decide to try a comeback, he had become a relic of a bygone era.
This match was the subject of last week's article in analyzing how Federer and Nadal have evolved since 2006.
It may have been the most important match in defining their rivalry and future encounters.
Federer was denied his first chance at a Fed Slam in this first media-hyped encounter with Nadal in a Slam final.
Many of the experts were divided on who would win, but most felt Federer's talent would continue to dominate.
For Federer, it would only become more difficult to capture the French Open. He also has had to deal with Nadal losses as the toughest part to an otherwise nearly flawless career.
If Federer had beaten Nadal, he would have had the Fed Slam and avoided the annual media circuses through 2009 wondering when and if he could win it. Furthermore, he might have been able to knock Nadal back from Wimbledon and the 2009 Aussie Open.
Instead, Nadal and his tenacity would never be denied in playing Federer like nobody else has. Much of this is the confidence with the success Nadal created on clay. Nadal would have won a few French Open titles regardless, but maybe he would only be standing at three or four in 2012.
Had Federer won in 2006, he may have won several more titles, possibly 20 Slams or more. Imagine if Federer continued to steamroll and overwhelm the likes of Nadal and young Djokovic well into the next decade. There would never again be other GOAT discussions people love and loathe so much.
In 1994, Agassi and new coach Brad Gilbert charted a course to get to No. 1. Agassi won the 1994 U.S. Open as an unseeded player, and defeated Pete Sampras at the 1995 Aussie Open. By April 1995, he had surpassed Sampras to achieve the No. 1 ranking.
But Agassi slipped in the French Open quarterfinals, and he blew a lead to Boris Becker at the Wimbledon semifinals.
Still, Agassi defeated Sampras three of five times on hardcourts (Aussie, Miami, Montreal) and rode a 26-game winning streak into the U.S. Open finals.
The U.S. Open wasn't Agassi's best day and Sampras once again rose to the occasion behind his big serve and clutch play. Sampras took the first two sets, and split the last two to close Agassi out.
In his autobiography, Open, Agassi admitted that the defeat crushed him. He had put so much into his crusade, and had again come up on the short end to Sampras.
Over the next few years, he was more unmotivated, and eventually dropped to No. 141 in the world. He used crystal methamphetamine and failed an ATP drug test.
Though Agassi revitalized his career in 1999, it was a reminder of what could have been. Perhaps the U.S. Open win could have sent Sampras into soul-searching. It's not unreasonable to suppose that Agassi could have matched Sampras' dominance.
Maybe Agassi wins five or six more Slams from 1996-1998. This could have put him at 14 Slams and a possible claim as the GOAT.
Sports consist of so many twists and turns in the careers and legacies of players and teams. We can only know for sure of what actually happened, but there will always be the "what if?" moments that define how fans think about the athletes and their careers.