Defending champion Novak Djokovic returned to action after a three-week break with victory over Spain's Nicolas Almagro at the Italian Open.
The world number one, who missed last week's Madrid Open to rest, beat Almagro 6-1 6-7 (5-7) 6-3 in Rome.
Djokovic, 27, will next face another Spaniard, Roberto Bautista Agut.
In women's action, top-ranked Serena Williams cruised past 39th-ranked Anastasia Pavlyuchenkova 6-1, 6-3 in just over an hour.
While Maria Sharapova led Jarmila Gajdosova 6-2 3-1 when the Australian retired.
"Madrid was really the start of my clay court season," said Sharapova, who reached the semi-finals last week.
"My preparations started a little bit later this year than in previous ones. I have to take my time and get into a groove, it's been a while since I've played that many matches within a span of six days."
Victoria Azarenka needed a visit from the doctor on court and made 16 double faults before seeing off Lucie Hradecka 7-5 2-6 6-1.
Djokovic became the first man to win the opening three ATP Masters 1000 events of the season when he took the Monte Carlo title last month, and extended his winning run to 18 matches against Almagro.
The Spaniard made him work hard for it, reeling off five points in a row to take the second set tie-break and holding firm in the decider until the seventh game.
Djokovic finally got the break when Almagro netted and the Serb converted his second match point to reach round three.
"In the important moments today I did feel a little uncomfortable. Maybe that's from lack of playing,'' Djokovic said. "I'm sure I'll be back on track in no time."
Eighth seed Stan Wawrinka battled past Juan Monaco 4-6 6-3 6-2, but ninth seed and US Open champion Marin Cilic went down 6-4 6-3 to Guillermo Garcia-Lopez.
Tomas Berdych of the Czech Republic beat Italian Matteo Donati 6-2 6-4.