Nadal, Federer, Djokovic and Murray all through in Rome

Roger Federer joined Novak Djokovic and Andy Murray in the third round of the Rome Masters on Wednesday with the Swiss admitting that he was fully expecting to lose against Alexander Zverev.

"I'm cautious but extremely happy - I was expecting to lose in straight sets today," admitted the 17-time Grand Slam champion, who withdrew last week from Madrid with back pain.

"That was the mindset going in. To win in straights is actually a really big surprise to me.

"I only decided after the warm-up that I was actually going to play. For me it was a big match on many levels."

The 89-minute match was the first for the 34-year-old Swiss since losing a Monte Carlo quarter-final to Jo-Wilfried Tsonga nearly a month ago.

Full screen

Even in victory Federer said that he would decide at the last minute whether he can take to the court on Thursday against 13th seed Dominic Thiem, a 6-3, 6-2 winner over Joao Sousa.

"I don't know how I'm going to feel tomorrow. I hope (I can play). I'm literally going practice after practices. It's baby steps right now."

Rome marks only the fourth tournament of the season for Federer, who underwent knee surgery in early February, the first operation of his career.

Federer broke for 4-2 on his way to collecting the opening set in 28 minutes.

The Swiss then earned a break in the third game of the second set but then lost serve for 2-all.

The veteran broke back on his fourth opportunity in the 11th game for a 6-5 lead and finished off the welcome win a game later, a drop shot setting up two match points with Zverev driving wide on the first.

Top seed Djokovic and number two Murray produced no-drama victories, with the Serb beating Stephane Robert 7-5, 7-5 while Murray put out Kazakh Mikhail Kukushkin 6-3, 6-3.

"Today was an extremely difficult match," Djokovic said. "Conditions were very tough, he was very unpredictable with his shots.

"Obviously he didn't have anything to lose, so he was going for some shots that were amazing.

"It wasn't easy for me to find my way through the match. When it mattered the most, I managed to make him play an extra shot and pull this one through."

Rafael Nadal continued his recent good form, beating Philipp Kohlschreiber 6-3, 6-3.

Australian Nick Kyrgios picked up another big win in an excellent season so far, putting out tenth seed Milos Raonic 7-6 (7/5), 6-3.

French 11th seed Richard Gasquet beat Andreas Seppi 6-3, 6-4.

In women's second-round play, Eugenie Bouchard handed second-seeded Australian Open champion Angelique Kerber a 6-1, 5-7, 7-5 defeat, her second straight in an opening match after losing last week in Madrid.

"In the first one-and-a-half sets I was completely not playing my game and I was completely not on the court," the German said.

"I was just trying to fight back. I was not playing my best tennis. But of course I was fighting and the third set was really close. At the end she played good and won the last point."

Spanish third seed Garbine Muguruza crushed Russian Ekaterina Makarova 6-1, 6-0 while Madrid quarter-finalist Irina-Camelia Begu of Romania upset injured fourth seed Victoria Azarenka 6-3, 6-2.

The Belarusian withdrew with lower back pain last week from Madrid.

"I was trying but it didn't work," Azarenka said. "The back is not good right now. I'm very disappointed obviously with that.

"I thought I was okay and was ready to play and came back, so I'm just disappointed. We'll see what happens."

Australian Daria Gavrilova dispatched Madrid champion Simona Halep, seeded sixth, 6-3, 4-6, 6-3.

American Madison Keys knocked out fifth seed and two-time quarter-finalist Petra Kvitova 6-3, 6-4, while Misaki Doi saw off French Open finalist Lucie Safarova 6-3, 7-5.

American 7-time major winner Venus Williams bowed out after a marathon defeat to Timea Babos that lasted nearly three hours.