Dustin Johnson withdrew from the 2020 CJ Cup on Tuesday after testing positive for COVID-19.
"Obviously, I am very disappointed," Johnson said in a statement. "I was really looking forward to competing this week, but will do everything I can to return as quickly as possible. I have already had a few calls with the Tour's medical team and appreciate all the support and guidance they have given me."
Johnson will be replaced by J.T. Poston in the event.
The CJ Cup, set to begin Thursday at Shadow Creek in Las Vegas, features the top 60-ranked players from the previous FedEx Cup season. Justin Thomas has won the event in two of its three years since it debuted in 2017.
Johnson ascended back to the world No. 1 spot after running away with the 2020 FedEx Cup. The 36-year-old finished no worse than sixth in any of his last four tournaments, taking home the Northern Trust and Tour Championship events.
It is unclear when Johnson will be available to return to the course.