San Francisco Frontiers - Sinner in derby with qualifier Pellegrino after strolling into Italian Open last 16

The world number one easily won his 25th straight match, taking just over an hour to see off Australia's Popyrin and give qualifier Pellegrino his moment on the big stage on Tuesday afternoon.

Pellegrino, 29, who beat 20th seed Frances Tiafoe 7-6 (10/8), 6-1, is ranked 155 in the world and before this week had never played in the main draw of a Masters 1000 tournament.

"It's fun to play a derby in Italy, he's having an incredible tournament with a lot of victories against some really good opponents," Sinner told reporters.

"We've played each other a long time ago (in 2019 in an ITF tournament), but he was a different player, and I was a different player."

Sinner meanwhile is trying to extend his own record-breaking run of overall victories in the ATP's top-ranked events after having won his last five.

The 24-year-old joins Novak Djokovic as the only player to win a year's first 25 Master 1000 matches, with the Serbian tennis icon's record run stretching to 31 matches in 2011.

Popyrin was suffocated by Sinner and made 23 unforced errors on his way to a comprehensive defeat.

The world number 60 only got 48 percent of first serves into play and that allowed Sinner to break five times and close out a match which was barely a contest.

Should Sinner prevail at the Foro Italico he will be the first Italian to win there since Adriano Panatta 50 years ago, and would complete his collection of Master 1000 tournaments.

"Sinner is different to everyone else at the moment, he is a class above," said Pellegrino.

"I'll try to give my best out there and above all enjoy the atmosphere out on the court."

With great rival Carlos Alcaraz out injured and Novak Djokovic eliminated early, Sinner will be red-hot favourite as he builds towards completing the career Grand Slam at the French Open which starts next week.

Former Rome champion Daniil Medvedev gets his tournament underway by winning an entertaining match with Pablo Llamas Ruiz 3-6, 6-4, 6-2, setting up a clash with Thiago Agustin Tirante who beat 10th seed and Rome native Flavio Cobolli 6-3, 6-4.

- Swiatek back to best? -

Iga Swiatek will face Jessica Pegula on the quarter-finals of the women's tournament after making short work of Naomi Osaka, beating the Japan star 6-2, 6-1 and looking more like the player that won four French Open titles.

Pole Swiatek hasn't won a clay court tournament since claiming her most recent title at Roland Garros two years ago, with personal problems a factor in her poor performances on her favoured surface.

But she looked back to her old self on Monday, giving Osaka nowhere to turn as she scurried around the court and finished off the match in just one hour and 22 minutes.

Osaka, a four-time Grand Slam winner, is yet to get beyond the last 16 of any tournament this year after also being knocked out of Indian Wells and the Madrid Open at the same stage by Aryna Sabalenka.

Coco Gauff survived a scare against Iva Jovic, coming back from a match point to win 5-7, 7-5, 6-2 and reaching the women's quarter-finals.

American star Gauff, who is reigning French Open champion and reached the final in Rome last year, won a draining match on windy centre court which took the best part of three hours.

Gauff was so annoyed with herself shortly after saving a match point against the serve at 5-4 down in the second set that she smacked herself in the head.

But she recovered to eventually see off her fellow American and set up a clash with Mirra Andreeva in the last eight.

B.Johnson--SFF