The two stars could clash in the semifinals.
Nadal, No. 4 in the world rankings, is seeded third in Paris after No. 2-ranked Andy Murray withdrew with a back injury.
Nadal has won the last three French Open titles and took four others from 2005-08. Paul Ayme (1897-1900) and Bjorn Borg (1978-81) are the only other players to have won the event four consecutive times. Nadal is looking to do it for a second time.
Nadal is also trying to match the all-time record for French Open titles. Max Decugis won the event eight times from 1903-14. The Open was first contested in 1891.
Nadal's efforts to win again could see a semifinal pairing against Djokovic, who is seeking his first French Open title, the only championship missing from a career Grand Slam. Nadal beat Djokovic in four sets in last year's Open final.
Nadal is 36-2 this year with six tournament titles and two runner-up finishes.
Djokovic is 28-4 with three championships, including the Australian Open.
Fellow Serb Janko Tipsarevic, seeded eighth, would be Djokovic's quarterfinal opponent if the draw plays to form. Seventh-seeded Richard Gasquet is the second-highest seeded player in Nadal's section.
World No. 3 Roger Federer, seeded second, won the French Open in 2009, completing his career Grand Slam, and has finished second to Nadal four times. His semifinal opponent could be fourth-seeded David Ferrer. Before that, if the tournament results follow the seedings, Federer would meet No. 6-seed Jo-Wilfried Tsonga in the quarterfinals. Ferrer would draw fifth-seeded Tomas Berdych.
Top 10 players missing from the men's draw are Murray and Juan Martin del Potro, who is out of the event due to a viral illness. With one U.S. Open title each, Murray and del Potro are the only players other than Djokovic, Federer and Nadal to have won a men's Grand Slam title since the 2005 Australian Open, a period covering 32 major tournaments.
The 2013 French Open begins Sunday and closes with the men's singles final June 9.