Clay king Rafael Nadal has admitted that he is nervous about his Wednesday start at the Monte Carlo Masters, a fortnight after quitting with knee pain prior to his last match.
"I'm scared because this is the start to an important season for me," said the Spaniard, who is bidding for an unprecedented eighth straight title on the clay of the principality. "Hopefully it will work well."
Nadal, seeded second behind Novak Djokovic, will play Jarkko Nieminen in the second round after the Finn beat Radek Stepanek 6-3, 7-6 (7-3).
In first-round play on Monday, all three seeds on court advanced.
Spain's number 13 seed Fernando Verdasco, a 2010 finalist against Nadal, beat Belgian Olivier Rochus 4-6, 6-2, 7-5, while 15th-ranked Austrian Jurgen Melzer defeated Lukas Kubot 6-2, 7-5.
Alexandr Dolgopolov, the number 16 seed, put out Argentine Juan Ignacio Chela 6-2, 6-2.
Frenchman Paul-Henri Mathieu, ranked 352 in the world after a long absence with a knee injury, crushed Donald Young 6-0, 6-1 to leave the American winless in his last five events.
Australian Bernard Tomic reached the second round by beating Denis Istomin of Uzbekistan 6-4, 6-3 to claim his first ATP-level victory on clay.
Tomic won a qualifying match in Moncao a year ago but lost out to Julien Benneteau for a spot in the main draw.
"I'm starting to learn how to play on clay, that's the important thing," said the 36th-ranked Australian.
"If I play my tennis, (clay specialists) struggle with my game even on clay."