Daly, known as "Wild Thing" during his heyday on the PGA Tour, withdrew on Sunday from the August 6-9 event, one of golf's four majors, which will be played at San Francisco's TPC Harding Park without spectators.

The 54-year-old, who won the event in 1991, is one of several players, including former World No.1 Lee Westwood and Italy's Francesco Molinari, to decide not to play.

"People keep asking why I (withdrew) from PGA???" Daly said on Twitter. "California now #1 in cases/deaths, I had knee surgery, I'm a diabetic & I don't feel comfortable flying.

"Being too close proximity to even small crowds & risk exposure with my health not worth it!"

The tweet marked a shift in tone from April when he joked about vodka and Diet Coke being a "cure" for COVID-19. He later said he meant no harm with his comment.