Rome: In the first of the second-round matches on Tuesday, Japanese sixth seed Kei Nishikori had to fight back from a set down to see off Serb Viktor Troicki 5-7, 6-2, 6-3.
Roland Garros holder Stan Wawrinka, the fourth seed in Italy, raced through the final two sets in beating Frenchman Benoit Paire 5-7, 6-2, 6-1.
Eighth seed Tomas Berdych cruised into round three with a 6-3, 6-4 victory over Albert Ramos of Spain.
Frenchmen Nicolas Mahut, Stephane Robert and Jeremy Chardy all won their first-round ties.
Belgian 12th seed David Goffin defeated Jack Sock 6-4, 6-4 and Juan Monaco put out South African 16th seed Kevin Anderson 3-6, 6-3, 6-2.
Serena Williams played her first match since late March in Miami, advancing to the third round after beating Anna-Lena Friedsam 6-4, 6-3.
"It wasn't an easy match, and she's an up-and-coming player and she plays well," 21-time major champion Williams said.
"I was really happy with my level. I think I was really mentally consistent.
"I started out fast. Those are some of the things I wanted to work on."
Madrid women's champion Simona Halep hopes to build on her Spanish success this week in the WTA Italian Open, after the Romanian beat Dominika Cibulkova at the weekend to win her first title in over a year.
"I didn't play the same at the beginning of the year, it was a tough period for me as I started the year a bit sick. I couldn't train like I do now," she said.
"But I came back very strong, in my opinion, and played good tennis in Madrid. I have more confidence - I believe in my game."
In the women's first round, ninth seed Svetlana Kuznetsova beat Caroline Garcia 7-5, 6-4, while Timea Bacsinszky crushed Belgian Yanina Wickmayer 6-2, 6-2.
Unseeded former Wimbledon finalist Eugenie Bouchard battled past two-time Rome winner Jelena Jankovic 6-4, 2-6, 6-3, and Briton Johanna Konta thrashed Johanna Larsson 6-1, 6-2.
Nadal bids for Rome title with possible Djokovic clash looming
Rafael Nadal said Tuesday that he is in confident mood ahead of his first match of the Rome Masters, despite his semi-final defeat to Andy Murray in Madrid last week.
The seven-time champion insisted that he is focusing solely on his second-round clash with Philipp Kohlschreiber on Wednesday, and not looking forward to a possible quarter-final against Novak Djokovic.
"I'm not playing Novak tomorrow. I'm going to play against (Philipp) Kohlschreiber. He's playing great. He won in Munich couple of weeks okay and played semi-finals in Barcelona too," fifth seed Nadal said.
"He's playing well and he's a very good player on clay. I am worried about that now."
Nadal won titles last month in Monte Carlo and Barcelona to start his pre-French Open clay campaign in the best possible way.
"My game is good, three tournaments, two victories (Monte Carlo, Barcelona), one semi-final. Tough tournaments, good victories, good matches. If I'm not happy now, I don't know when I gonna be happy," he said, after a training session on the Italian clay that plays similar to that of Roland Garros.
Kohlschreiber has just a single win over Nadal - on the grass in Halle - against 13 losses to the Spaniard, with six of them coming on clay.
The 26th-ranked German beat Spain's Inigo Cervantes in the Rome first round 6-4, 6-2.
Madrid winner Djokovic hopes he can maintain his excellent form this week as the French Open, the only Grand Slam title that has eluded him so far in his career, draws closer.
"I'm just hoping I can carry on the high quality of performances I have had throughout the week in Madrid and also this week in Rome, find that freshness and get as far as I can," the world number one said.
"Once I step on the court, I don't know how to pace myself. I'm on the court to get the job done, to try to win.
"It would be disrespectful to the tournament and to all the people that come to watch you that, if you are thinking of some other tournament that's ahead of you. So that's not in my mind."
Updated Date: May 11, 2016 10:44 AM