Nick Kyrgios pulled out of the ATP Winston-Salem Open on Sunday night, paving the way for Andy Murray to breeze into the second round with a dominating win over lucky loser Noah Rubin.

After a slow start to the first set, the former world number one Murray found his form and cruised through his opening match, beating Rubin 6-2, 6-0 in just 58 minutes.

Murray was initially scheduled to face Kyrgios but the Aussie withdrew just before the start of their match, throwing Sunday's schedule into chaos.

Murray will next face 13th seeded Frances Tiafoe, who received a bye into the second round.

Organizers gave Murray several different scenarios before finally deciding he would face American Rubin, who had to play back-to-back matches with just an hour rest between them.

"It was a strange 45 minutes before I played this match," said the Scot. "I didn't know if I would be playing tonight.

"They said I would play a qualifier and wouldn't play until tomorrow. And then they said I would play a lucky loser. So my opponent change three times in 45 minutes.

"Unfortunately for (Rubin) he had to play a tough match in the heat and then had to come out again."

Rubin took the court after falling to France's Lucas Pouille in a two-hour qualifying final.

The 34-year-old Murray has had to battle injuries of his own, with his latest one being a groin problem. But that didn't seem to be a factor against Rubin as Murray blasted 11 aces and had just three double faults.

Kyrgios withdrew saying he had been bothered by pain in his left knee for some time. He said he would rather rest for the upcoming US Open than aggravate it at a regular tournament.

"Obviously I had to look after my body and with a Grand Slam next week," he said. "I have been dealing with knee pain the last couple of weeks.

"With the US Open just around the corner I just didn't feel this was worth the risk of going out there and possibly making it worse."

Kyrgios and Murray were set to square off for the seventh time overall with Murray holding a commanding 5-1 series lead.

"I have been in Florida rehabbing and training and I came here excited to play Andy Murray one of my good friends," said Kyrgios, who stood for his new conference with a cloth medical wrap on his left knee.

Kyrgios' only win over Murray came in their most recent match three years ago at the Queen's Club, where Murray made his return following his first hip surgery.

"I had a bit of a hit to see how it is today," Kyrgios said. "I got another week now (until the US Open)."

Kyrgios retired from his third-round match at Wimbledon with an abdominal injury. He opted out of the Olympics in part because of lack of fans.

He lost in his opening matches at Washington and Toronto in recent weeks and this would have been his fifth tournament of the year outside of Australia.