Brooks Koepka’s knee injury is bad enough that he withdrew from the Presidents Cup three weeks before it begins.

Koepka, the No. 1 player in the world who led all qualifiers for the American team, said Wednesday the injury he suffered Oct. 18 at the CJ Cup in South Korea is not recovering well enough for him to complete Dec. 12-15 at Royal Melbourne in Australia.

U.S. captain Tiger Woods replaced him with Rickie Fowler.

“I consider it to be a high honor to be part of the 2019 team and I regret not being able to compete,” Koepka said in a statement. “Since my injury in Korea, I have been in constant contact with Tiger and assured him that I was making every effort to be 100% in time for the Presidents Cup in Australia. However, I need more time to heal.”

Koepka was coming off a season in which he won three times, including a second straight PGA Championship, and had runner-up finishes in the Masters and U.S. Open. When he started the new season in October at Las Vegas, he revealed he had stem cell treatment on his left patella the day after the Tour Championship because his knee had been bothering him over the last five months of the season.

Two weeks later, he was walking down a slope off the tee at the par-5 third hole in the second round of the CJ Cup when his right foot hit a wet piece of concrete and he landed hard on his left knee for support. He shot 75 and withdrew after the round, returning to Florida for treatment.

Koepka has not spoken publicly about the nature of the injury. He was in touch with Woods, who had been contemplating alternative plans.

“Brooks and I talked, and he’s disappointed that he won’t be able to compete,” Woods said. “I told him to get well soon, and that we’re sorry he won’t be with us in Australia. He would clearly be an asset both on the course and in the team room.”

Woods, who used one of his four captain’s picks on himself after winning in Japan, originally left Fowler off the team and said it was the hardest phone call he made when telling prospective players he was not taking them.

Fowler, who got married in the offseason, has not played since the Tour Championship on Aug. 25 and withdrew from the Mayakoba Golf Classic last week because of a stomach bug he picked up during his honeymoon.

He is in the field for the Hero World Challenge in the Bahamas the week before the Presidents Cup.

“When I heard Brooks wasn’t going to be ready to play, I was bummed for him and the team,” Fowler said. “Then I got a call from both Brooks and Tiger. I was humbled and excited to be given the chance. To be picked by Tiger to compete with him and the rest of the team is very special. It is impossible to replace the world’s No. 1, but I can assure my teammates and American golf fans that I will be prepared and ready to do my part to bring home the Presidents Cup.”

Koepka had not entered the Hero World Challenge. It remained unclear whether he would be fit in time for the Sentry Tournament of Champions on Jan. 2-5 in Kapalua, or whether he would return to the Saudi International later in January.

Fowler has played on the last two Presidents Cup teams, going 2-0-1 in team play with Justin Thomas at Liberty National in 2017. Among other U.S. players on this team, Fowler previously has played with Patrick Reed and Dustin Johnson.