Rome,  Top seeds Novak Djokovic and Rafael Nadal have entered the quarterfinals of the Italian Open with straight-set wins in their respective third-round matches.

On Friday, Djokovic defeated his fellow Serb Filip Krajinovic 7-6 (7), 6-3 to enter the last eight of the tournament for the 14th straight year.

"It was definitely one of the longest sets I think I have ever played," said Djokovic as per the ATP Tour website after the match. "Never easy, I think, emotionally to play against someone that is one of my best friends for many years...I think the first set could have gone a different way, as well.

"Fortunately for me it went my way and that allowed me to swing through the ball a bit more in the second set. Maybe physically and mentally, he dropped a level and I used my opportunities and capitalised to win in straight sets."

In other Round of 16 match, nine-time champion Nadal cruised past 2019 Monte-Carlo Masters finalist Dusan Lajovic 6-1, 6-3 to reach his 15th Rome quarter-final.

"I played at I think a very positive level of tennis. Of course it needs to keep improving. I need to keep working on a couple of things that are not coming automatically. But I can't ask for more," Nadal said. "(It was) another great evening for me against another good opponent. Can't complain at all. Much better (than) what I expected."

Lorenzo Musetti, 18, who had upset three-time Grand Slam champion Stan Wawrinka and Japan's top player Kei Nishikori in the tournament's opening two rounds, lost to Dominik Koepfer of Germany 6-4, 6-0.

Fourth-seeded Matteo Berrettini defeated Stefano Travaglia 7-6 (5), 7-6 (1) in an all-Italian contest to reach the last eight.

In the women's draw, top-seed Simona Halep beat Ukraine's Dayana Yastremska 7-5, 6-4. Second seed Karolina Pliskova registered a 6-4, 6-3 win over Russia's Anna Blinkova.

Former world number one Victoria Azarenka advanced to the quarterfinals as her opponent Darya Kasatkina of Russia retired during the first set with the scores at 6-6.Ninth-seeded Garbine Muguruza eased into the final eight as she Johanna Konta of Great Britain 6-4, 6-1.