Monaco - Ninth-seeded Marin Cilic overcame a shaky serving performance to beat Horacio Zeballos of Argentina 6-2, 6-7 (6/8), 6-2 in the first round of the Monte Carlo Masters on Monday.
Cilic looked set for an easier win after converting all three of his break points in the first set, before both players dropped serve three times in the second set. Cilic stepped it up in the third, hitting three aces and breaking Zeballos's serve twice.
He next plays either Jerzy Janowicz of Poland or South Africa's Kevin Anderson in the second round. They play their match on Tuesday.
VIDEO: Marin Cilic v Horacio Zeballos, highlights
Earlier, 12th-seeded Milos Raonic beat Julien Benneteau 6-1, 6-4 and Roberto Bautista-Agut upset No 11 Gilles Simon of France 6-3, 7-6 (6).
Canadian Raonic served 15 aces and broke his French opponent three times to set up a match against Jarkko Nieminen, who thrashed Viktor Troicki 6-1, 6-2.
"A lot of things I did well, especially only having a limited amount of preparation before here," said the 22-year-old Raonic, who improved to 14-4 this season, and hit one booming second serve ace clocked at 201 km/h.
Raonic lost his only match against Nieminen in the quarte-rfinals of the Thailand Open in Bangkok last September.
"I didn't do so well, did a lot of things poorly in that situation," Raonic said. "If I play and I keep going for it like I was today - I was able to dictate play a bit - I think if I can get ahead in the points, I can keep that advantage and I think I'm pretty good in that position."
Bautista-Agut was pushed a little harder, closing it out on his fifth match point when Simon hit a forehand into the net. The Spaniard will play either Florian Mayer or Benjamin Balleret.
"I didn't produce anything during that first set. In fact, I was tired. Long rallies were killing me," Simon said. "In every game I was giving him a couple of free points, which hurts a lot on clay because from his side there were not many free points."
It was Simon's fourth straight defeat after losing to Tommy Haas in the Sony Open quarter-finals and both singles matches in France's Davis Cup quarter-final loss to Argentina.
Fabio Fognini came from behind to down 15th-seeded Andreas Seppi 3-6, 6-4, 6-4 in an all-Italian match after converting seven of 10 break point chances. He faces either Radek Stepanek or qualifier Albert Ramos.
In other first-round matches, there were wins for Nikolay Davydenko, qualifier Pablo Andujar and French pair Benoit Paire and Edouard Roger-Vasselin.
Davydenko beat qualifier Daniel Brands 6-3, 6-4; Andujar scraped past Jeremy Chardy 6-7 (4/7), 7-5, 6-2; Paire won 6-4, 6-4 against Ivan Dodig, and Roger-Vasselin topped Robin Haase 6-3, 6-2.
Top-seeded Novak Djokovic will decide on Tuesday whether he's recovered from his ankle problem to play Mikhail Youzhny of Russia on Wednesday, when No 2 Andy Murray takes on Roger-Vasselin and eight-time defending champion Rafael Nadal faces either 2010 finalist Fernando Verdasco of Spain or Australian Marinko Matosevic.
Latest results from the Monte-Carlo Masters on Monday (x denotes seeding):
First roundMarin Cilic (CRO x9) bt Horacio Zeballos (ARG) 6-2, 6-7 (6/8), 6-2
Mikhail Youzhny (RUS) bt Daniel Gimeno-Traver (ESP) 6-4, 6-0
Milos Raonic (CAN x12) bt Julien Benneteau (FRA) 6-1, 6-4
Jarkko Nieminen (FIN) bt Viktor Troicki (SRB) 6-1, 6-2
Fabio Fognini (ITA) bt Andreas Seppi (ITA x15) 3-6, 6-4, 6-4
Benot Paire (FRA) bt Ivan Dodig (CRO) 6-4, 6-4
Roberto Bautista-Agut (ESP) bt Gilles Simon (FRA x11) 6-3, 7-6 (8/6)
Pablo Andujar (ESP) bt Jeremy Chardy (FRA) 6-7 (4/7), 7-5, 6-2
Nikolay Davydenko (RUS) bt Daniel Brands (GER) 6-3, 6-4
Edouard Roger-Vasselin (FRA) bt Robin Haase (NED) 6-3, 6-2