SHANGHAI - World No. 1 Jannik Sinner beat American Ben Shelton with a 6-4, 7-6 (1) straight-set win in the fourth round of the ATP Shanghai Masters on Wednesday.

In the opening set, facing an aggressive start from Shelton who created two break points at 2-1, Sinner showed his resilience. In the ninth game, the Italian finally found an opportunity to embrace his first break point of the match and successfully converted it into a 5-4 lead.

When it comes to the decisive tie-break in the second set, Shelton notched the opening point on serve, but Sinner never gave his opponent any chance later by striking his best balls at critical moments to win seven consecutive points.

"Obviously, we cannot take only one match. I think it was a very tough match today. He had chances in the first and second sets," said Sinner. "I'm happy how I handled this situation. Obviously I reached the position where I have been last year, but it is different. So I'm happy to be in the position where I am."

The 23-year-old has reached the quarters in all 14 tournaments he has entered this season. About the secret of his consistency, Sinner said he tries to accept every challenge he meets. "There are always very tough times on court. You have to be mentally ready to go against them. That's exactly what I'm trying to do," he added.

Elsewhere, Carlos Alcaraz also outlasted Gael Monfils to enter quarterfinals by sealing a 6-4, 7-5 victory. The Frenchman had beaten Alcaraz at the Cincinnati Open in August.

Alcaraz was optimistic about the result in Shanghai after clinching the title at the China Open. "I'm feeling great and physically have not too many problems. I'm playing great tennis lately, so I have a lot of confidence to go further in this tournament," he said.

Also on Wednesday, Novak Djokovic secured an easy 6-3, 6-2 triumph over Roman Safiullin to reach his 10th quarterfinals of the Shanghai Masters.