MADRID, Spain (AFP) — Jannik Sinner continued his quest to become the first man in history to win five Masters 1000 tournaments in a row with a smooth 6-2, 6-3 victory over Danish qualifier Elmer Moller at the Madrid Open on Sunday.

The world No. 1 extended his winning streak to 19 matches, a run that began early March in Indian Wells, and he has also captured 24 consecutive victories at the Masters 1000 level, dating back to the Paris Masters last October.

Searching for a maiden title at this level on clay, Sinner advanced to the Round of 16 at the Caja Magica with a 77-minute performance against the 169th-ranked Moller.

The Italian broke Moller four times and dropped serve just once late in the opening set to book a Last-16 meeting with Cameron Norrie.

"I tried to stay calm, trying to serve well in the important moments," Sinner told Tennis TV on court after the win.

"I think today that was the key. And not a lot of rhythm, so I tried to stay quite compact."

Another Italian enjoyed a successful Sunday in the form of Lorenzo Musetti, who overcame Dutch 29th seed Tallon Griekspoor 6-4, 7-5.

The sixth-seeded Musetti will face Czech 11th seed Jiri Lehecka for a spot in the quarterfinals.

In night session WTA action, world number two and reigning Australian Open champion Elena Rybakina shook off a stubborn Zheng Qinwen, knocking out the Olympic gold medallist 4-6, 6-4, 6-3 to reach the Round of 16.

In a rare moment of frustration, the usually calm and collected Rybakina argued with umpire Julie Kjendlie late in the second set over a mark on the court, which she felt clearly indicated a Zheng serve was out but was deemed in by the electronic line-calling system.

"Are you kidding me? This is not a joke. The system is wrong," argued Rybakina, but her protests were in vain because Kjendlie is not permitted to leave her chair, check a mark and overrule the electronic line-calling system.