WASHINGTON, Aug 23, 2021 (BSS/AFP) - Australia's Nick Kyrgios withdrew from the ATP Winston-Salem Open on Sunday night with a knee injury, just moments before a scheduled opening round clash with former world number one Andy Murray.

Kyrgios said he had been bothered by pain in his left knee for some time and said he would rather rest and be healthy for the upcoming US Open than aggravate the problem at a tune-up tournament.

"Obviously I had to look after my body and with a Grand Slam next week, I wanted to be more cautious," 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 was replaced in the draw by lucky loser Noah Rubin, who took the court Sunday night against Murray shortly after falling to France's Lucas Pouille in a qualifying final.

The winner of the match faces off against 13th seed Frances Tiafoe, who got a bye into the second round.

Kyrgios and wild card 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, but obviously I have to look after my body," 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 the Scot made his return following his first hip surgery.

"I had a bit of 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.