World No. 1 Novak Djokovic came from behind in order to win his fourth-round match, while seven-time champion Rafael Nadal was an easier winner Monday at the French Open.
Last year's Roland Garros runner-up Djokovic dropped the first set on Day 9 of the fortnight before charging back to dismiss 16th-seeded German Phillip Kohlschreiber, 4-6, 6-3, 6-4, 6-4, in 2 hours, 42 minutes, while the third- seeded former top-ranked Nadal celebrated his 27th birthday by predictably blowing past 13th-seeded rising Japanese Kei Nishikori, 6-4, 6-1, 6-3, in just over two hours on the famed red clay on Court Chatrier.
Following his win, the crowd serenaded Nadal with a rendition of 'Happy Birthday' and he was presented with a large cake on court.
In the Djokovic-Kohlschreiber affair, the German secured the lone break of the first stanza to grab a one-set lead, but the Serbian star, who angrily busted his racquet during that first set, recorded the only breaks en route to claiming the second and third sets and broke Kohlschreiber by a 2-1 margin in the fourth en route to victory.
The 26-year-old Djokovic is now third on the men's Open Era list with 16 straight trips into a Grand Slam quarterfinal.
Djokovic played for the first time after learning over the weekend that his childhood coach and the person who first recognized his exceptional talent, Jelena Gencic, died in Belgrade on Saturday at the age of 77.
The mighty Djokovic reached his first-ever French Open final last year, only to lose to the great Nadal. The reigning Australian Open champ needs Roland Garros to complete a career Grand Slam.
Djokovic's quarterfinal opponent will be resurgent German Tommy Haas, who looked impressive in a straight-set rout of Russian Mikhail Youzhny.
Meanwhile, the 11-time major titlist Nadal, seeking a fourth straight title at this lone clay-court Slam, improved to 56-1 lifetime at Roland Garros on Monday. The Spanish strongman has been brilliant so far in 2013, going 40-2 with six titles in eight events.
Nadal broke Nishikori five times, while Nishikori failed to break the clay court stalwart on Day 9.
The formidable left-hander Nadal will meet Swiss Stanislas Wawrinka on Wednesday, as the ninth-seeded Wawrinka upended seventh-seeded French crowd favorite Richard Gasquet in an epic five-setter, 6-7 (5-7), 4-6, 6-4, 7-5, 8-6.
Nadal topped Wawrinka in an ATP Masters final in Madrid last month.
When asked how he came back from two-sets-to-love down against Gasquet, Wawrinka said, "I don't know."
Wawrinka prevailed in 4 hours, 16 minutes on Court Lenglen against a distraught Gasquet.
The aforementioned oft-injured Haas cruised to a 6-1, 6-1, 6-3 victory over Youzhny in just 90 minutes to reach the quarterfinals at Roland Garros for the first time. He has been to at least the round of eight in each of the other three Grand Slams.
In addition, the 35-year-old German became the oldest quarterfinalist in a major since Andre Agassi at the 2005 U.S. Open and became the oldest French Open quarterfinalist since a 39-year-old Istvan Gulyas in 1971. He is also the first German in the French quarters since Michael Stich and Bernd Karbacher in 1996.
"These are cool stats sometimes to hear," said Haas, who has undergone shoulder, elbow and hip surgeries during his career. "I feel like I'm riding a wave that I hope to continue as long as I can. I'm going out there and I try to improve my game as much as I can, and to be in this situation is spectacular."
The 12th-seeded Haas, a champion in Munich last month, needed 13 match points to finally finish off John Isner in the third round on Saturday, but had little trouble against Youzhny. The Russian beat Haas in the first round of the Italian Masters last month and took the first game on Monday, then proceeded to lose 10 straight on his way to a quick exit.
Youzhny was so frustrated on Monday that he demolished his racquet by banging it nine times against his changeover chair.
"Bad luck for that racquet," Youzhny said afterward.
The quarterfinals will get underway Tuesday, as second-seeded former No. 1 Roger Federer will take on sixth-seeded French favorite Jo-Wilfried Tsonga and fourth-seeded Spaniard David Ferrer will battle 32nd-seeded fellow Spaniard Tommy Robredo.
Federer is 9-3 lifetime against the former Aussie Open runner-up Tsonga, including a quarterfinal victory at the Aussie Open back in January. Ferrer is 6-2 all-time versus Robredo, as the two compatriots will meet for the first time at a major event.
The amazing Federer holds the men's record with 17 Grand Slam singles titles, including last year's Wimbledon championship and the 2009 French Open. The Swiss legend is also a four-time French Open runner-up to Nadal.