Jannik Sinner kept his US Open title defence on track Saturday as Iga Swiatek struggled through to the last 16 and home favourite Coco Gauff booked a blockbuster clash with Naomi Osaka.

Sinner rallied from a set down to beat Denis Shapovalov 5-7, 6-4, 6-3, 6-3 and is trying to become the first man to retain the title in New York since Roger Federer in 2008.

"I was in a very difficult moment today," said Sinner. "The scoreline was a bit against me today, but I just tried to stay there mentally."

World number one Sinner awaits the winner of the evening session match between US 14th seed Tommy Paul and Alexander Bublik, the 23rd seed from Kazakhstan.

"Week two is completely different. It's getting tougher and tougher, also physically and mentally," said Sinner.

To illustrate that point there were three more retirements in the men's draw on Saturday after the injury-induced exit of sixth seed Ben Shelton the day before.

Alex de Minaur, Lorenzo Musetti and 435th-ranked Swiss qualifier Leandro Riedi all moved on when their opponents........

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