This hot rivalry between tennis greats might be unmatched in any other sport. Aside from the exciting tennis it has produced in extremely meaningful matches, it has been distinguished by a graciousness on the part of both players.

Roger Federer was ranked No. 1 in the world for 237 consecutive weeks, starting in 2004, a mark no one may ever beat. He's won a record 16 Grand Slam singles titles, and the Swiss tennis player has won the career Grand Slam--cumulatively winning the four most important tennis tournaments, the French Open, Wimbledon, the US Open and the Australian Open--four times over. Federer has appeared in 23 Grand Slam tournament finals, another record.

Federer is considered one of the greatest tennis players of all time, but he's been bested by Rafael Nadal in 16 of their 24 meetings. The two players were ranked No. 1 and No. 2 for six consecutive calendar years from 2005 to 2010. All but one of their Grand Slam finals losses were to each other, the exception being Federer's loss to Juan Martin del Potro in the 2009 US Open. Now that's a rivalry.

Although they have battled each other for the top spot for seven years, the two players are friendly in their competitiveness. When their rivalry started to gain a lot of press, Nadal and Federer organized matches against each other with the proceeds benefiting their chosen charities. Nadal, who is five years younger than Federer, has said that Federer served as a role model for him. But the youngster has overtaken the greatest--Nadal is currently ranked No. 1 in the world, and Federer is No. 3

As the two battle for the French Open title in Paris, we remember three of their greatest clashes.

When Federer lost the 2009 Australian Open final to Nadal, it meant something bigger than another L to his rival. It snapped his streak of consecutive Grand Slam titles at 13, preventing him from catching Pete Sampras at 14. Federer was devastated, and he cried as the trophy was given to Nadal. Nadal responded by saying, You are one of the best players and it is always a pleasure playing against you. Remember, you're a great champion, you're one of the best in history. You're going to improve on the 14 of Sampras.

The 2008 Wimbledon finals are considered by some to be the best tennis match ever. Nadal took the first two sets relatively easily, but Federer clawed back and made the rest of the match a tight fight. Federer won the third set in a tiebreaker and forced a tiebreaker in the fourth as well, then fended off Nadal's two championship points and won it. In the fifth set, play was halted at 2-2 due to rain. The momentum had switched to Federer, but the delay allowed Nadal to get back on his game. He outlasted Federer to win Wimbledon 6-4, 6-4, 6-7, 6-7, 9-7. It was the longest final on record, at 4 hours and 48 minutes, and the last point was played in near darkness.

On May 2, 2007 the two played an exhibition match called the Battle of the Surfaces, in which half the court was clay and the other half grass. Nadal had always had an edge on Federer on clay, in particular in the French Open, which Nadal won every year from 2005 to 2008. He has beaten Federer on clay all six times the two have played five-set matches on the surface, and has won 11 of 13 on clay overall. Nadal won the match in front of fans on his home island of Mallorca, 7-5, 4-6, 7-6 (12-10). Federer scored an equal amount of points on both surfaces, while Nadal scored 12 more points on clay and seven fewer points on grass.