Seven-time champion Rafael Nadal looks to celebrate his 27th birthday on Monday by reaching the French Open quarter-finals, while world number one Novak Djokovic faces up to a ghost of the past.
Nadal, bidding to be the first man to win the same Grand Slam title eight times, plays Kei Nishikori who is trying to become just the second Japanese man to reach the last eight after Jiro Satoh, who made the quarter-finals in 1931 and 1933.
Nadal, the third seed, has a 55-1 winning record at the French Open, but his passage to the fourth round has been far from convincing after dropping the opening sets of his first two rounds for the first time in his career.
But since returning from a seven-month injury lay-off in February, the Spaniard has built up an impressive run of six titles in eight finals.
He has also won 34 of his 36 matches on clay in 2013 -- he lost to Horacio Zeballos in his first tournament back at Vina del Mar in February before seeing his eight-year winning streak at Monte Carlo ended by Djokovic in April.
Nishikori, the 13th-seed, is already the first Japanese man to reach the last 16 in Paris since Fumiteru Nakano in 1938.
Top seed Djokovic, who needs a French Open to become only the eighth man to claim a career Grand Slam, takes on German 16th seed Philipp Kohlschreiber.
Significantly it was a 2009 defeat to the German in the third round which helped Djokovic become the force that he is today.
He is bidding to reach his 16th consecutive Grand Slam quarter-final -- the last time he failed to reach the last eight at a major was at 2009 Roland Garros.
Tommy Haas, the 35-year-old 12th-seeded German, plays Russia's Mikhail Youzhny, looking to become the oldest Grand Slam quarter-finalist since Andre Agassi at the 2005 US Open.
If he defeats Youzhny, the 29th seed on Court Suzanne Lenglen, he will also become the third German man to complete a set of Grand Slam quarter-final appearances.
Roland Garros will have at least one new quarter-finalist as Richard Gasquet, the French seventh seed, and Stanislas Wawrinka, the ninth seed from Switzerland, face each other.