The all-Australian clash at the World Tennis Tournament went the way of the higher-ranked de Minaur 6-1 6-4, with the highlight moment coming in the eighth game of the second set.

With Millman in control of the long really and dictating the play, de Minaur on multiple occasions was forced to play defence and simply keep the ball in play with a series of slice backhands and even forehands as he was stretched to all parts of the court.

The rally culminated when a short reply allowed Millman to find an angle on a forehand that dragged de Minaur wide of the tramlines but he somehow, on the dead run and lunging, swatted a forehand winner down the line.

The sensational shot left Millman dropping his racquet in utter disbelief, and the commentator wondering just what he had just witnessed.

"Oh, goodness me. You have go to be kidding me," the commentator said.

With no crowd in the stands due to COVID-19 restrictions, a stunned Millman was picked up by the court microphones.

"Hell of a shot that," Millman said.

As Millman picked up his racquet and glanced at de Minaur in awe, the commentator added: "An incredible exchange. Marathon rally. How on earth has he produced this, to win the point?"

World No.23 De Minaur, who lifted his fourth ATP Tour trophy in January at the Antalya Open, won 23 of his 27 first-service points against Millman and moves on to face Japan's Kei Nishikori in the second round.

Australian Open semi-finalist Stefanos Tsitsipas continues his impressive start to the year with a hard-fought 7-6 (7-4) 7-5 victory over Egor Gerasimov in his tournament opener.

Second-seeded Greek Tsitsipas was calm throughout the almost two-hour match to prevail and improve his record in 2021 to seven wins and one loss.

Fourth seed Andrey Rublev advanced to round two with a 7-6 (7-1) 6-3 defeat of American qualifier Marcos Giron, to set up a meeting with former world No.1 Andy Murray.

Their only previous meeting came at the Australian Open in 2017, when a 19-year-old Rublev won just five games.

"He destroyed me once already," Rublev said.

"I hope it's going to be a great match. I hope we're going to have great rallies, great fight."

Eighth-seeded Stan Wawrinka's disappointing start to the season continued as he was beaten 6-4 7-5 by Rublev's Russian compatriot Karen Khachanov.

Meanwhile, Poland's Hubert Hurkacz saw off the experienced Adrian Mannarino 6-3 7-6 (8-6) while Jeremy Chardy squeezed past fellow Frenchman Ugo Humbert 4-6 7-6 (7-5) 7-6 (7-4).

Australian Associated Press