Cincinnati, OH, USA, 16 August 2017 | AAP

Nick Kyrgios is into the second round of the Cincinnati Masters ATP event, grimacing and limping his way to a 6-2 6-3 win over Belgium’s David Goffin.

Kyrgios served 10 aces in the 66-minute victory, but appeared to still be struggling with fitness as he works his way back from a hip injury that led to him withdrawing from defending his title at the Atlanta Open in July.

The 22-year-old Australian won the first set after 31 minutes and despite the world No.23 at times struggling with his movement, it was his world No.13 opponent who called for the trainer at the end of the set.

Goffin received treatment to his upper left leg, as Kyrgios sat slumped in his chair underneath the umbrella.

Kyrgios went on to control the second set and held serve to love to close it out 6-3, maintaining the edge he holds over Goffin, who he beat in the final of the Tokyo ATP event last year and in Miami this year.

He now leads their head-to-head series 3-0.

“I knew it was going to be very tough,” Kyrgios said of the first-round Cincinnati match-up.

“He obviously wasn’t at 100 per cent today, but you know I’m not at 100 per cent either so it was a bit of a battle.

“But I served well at crucial moments. I’m feeling OK. I think as long as I can keep putting in performances like these and being able to compete I think I’m OK.”

Kyrgios will play Alexandr Dolgopolov in the second round after Dolgopolov beat Kevin Anderson 6-4 7-6(6).

The only other Australian in the men’s singles draw, qualifier John-Patrick Smith, lost his first-round match 6-4 6-4 to Richard Gasquet on Monday.