Sixteenth-seeded Philipp Kohlschreiber of Germany, Alexandr Dolgopolov of Ukraine and Grigor Dimitrov of Bulgaria all won in straight sets in the first round of the Monte Carlo Masters on Sunday.
Kohlschreiber broke Brazilian Thomaz Bellucci's serve five times in a 6-4, 6-2 win; Dolgopolov saved all three break points he faced in a 6-2, 6-4 win against Bernard Tomic, and Dimitrov broke Xavier Malisse twice in each set on his way to a 6-3, 6-2 win against the Belgian.
Dolgopolov broke Tomic's serve to improve to 5-1 overall against the Australian and he faces fifth-seeded Juan Martin del Potro of Argentina in the second round.
Dimitrov next plays No. 8 Janko Tipsarevic of Serbia, while Kohlschreiber plays either Frenchman Jeremy Chardy or a qualifier.
Top-ranked Novak Djokovic was set to later confirm whether he will take part in the tournament after twisting his ankle last weekend. He was included in the main draw.
Djokovic twisted his ankle while hitting a forehand early into his win against Sam Querrey of the United States during a Davis Cup quarterfinal.
He resumed light training on Friday with his coach Marian Vajda for a little under an hour, and he also had a short exhibition against second-ranked Andy Murray in an friendly match on Saturday.