World number one Roger Federer faces a potential third-round showdown with three-times winner Gustavo Kuerten in a tough opening week at the French Open.
Third seed Rainer Schuettler was the only high-profile casualty on the first day of the Rome Masters on Monday when he lost 6-2, 2-6, 7-5 to America's Vincent Spadea.
Spain's Feliciano Lopez sent the Australian ninth seed spinning out of the Madrid Masters on a night of surprises.
The duo are pairing up since their respective partners Max Mirnyi and David Rikl have opted out of the Long Island event.
The 16-year-old wild card at the Monte Carlo Masters won 7-5, 6-3.
The 31-year-old triumphed despite suffering from an apparent muscle problem to became the lowest seeded player, at 13, to claim the title since Gustavo Kuerten in 1999.
Beatriz Haddad Maia became the first Brazilian woman in 55 years to reach the quarter-finals
The 20-year-old Ostapenko was the first unseeded woman to lift the Suzanne Lenglen Cup since Britain's Margaret Scriven in 1933.
Alexander Zverev became the first German to reach the last four at the ATP Finals for 15 years as he beat American John Isner 7-6(5), 6-3 at the O2 Arena on Friday.
Factbox on Latvian Jelena Ostapenko, who beat Romania's Simona Halep 4-6 6-4 6-3 to win the French Open on Saturday and claim her first grand slam title:
After two weeks of intriguing tennis where the world's best fought hard to assert their dominance on clay, we have the champions out there.
Not since Stan Wawrinka's 2016 US Open triumph has a Grand Slam been won by someone other than the 'Big Three', winners of the last 13 major titles.
List of French Open men's singles champions:
Briton Andy Murray will take over from Novak Djokovic as World No 1 when the rankings are updated on Monday after his Paris Masters semi-final opponent Milos Raonic withdrew with a leg injury on Saturday.
The 2nd major of the year, the French Open will start on the weekend. With the clay-court grand slam starting on Sunday, here is the list of French Open champions over the years
Argentina's Diego Schwartzman ended a two-year wait for his second ATP tour title as he overpowered an exhausted Fernando Verdasco to win the Rio Open 6-2, 6-3 on Sunday.
The 20-year-old, looking to become the first unseeded woman to lift the Suzanne Lenglen Cup since 1933, blazed her way to the final, hitting winners and errors with reckless abandon.
A year after losing to Czech Lukas Rosol in the second round, French Open champion Rafael Nadal was outplayed by the 135th-ranked Steve Darcis on Court One, losing 7-6(4), 7-6(8), 6-4 in front of a disbelieving crowd at Wimbledon.
List of French Open men's singles champions:
It was the 31-year-old Serb's second comfortable win in the Gustavo Kuerten group and combined with Marin Cilic's 6-7(2), 6-3, 6-4 defeat of American John Isner later in the day, he sealed his place in the semi-finals at the year-ender for the eighth time.
In the earlier match, Zverev beat Cilic -- the Croat's 9th loss in 10-round robin matches in the Finals
Having dug in early on to stay with Federer, Nishikori ended up running away with the match to inflict a first straight sets defeat in the ATP Finals round-robin stages on the 20-time Grand Slam champion.
