Brooks Koepka has withdrawn from the Presidents Cup with a knee injury and been replaced by Rickie Fowler.
World number one Koepka had been a doubt since dropping out of last month's CJ Cup at Nine Bridges but was named in Tiger Woods' United States line-up for December's team event in Melbourne.
The four-time major winner revealed he had undergone a stem cell procedure on his left knee during his off-season break following a partially torn patella tendon.
And on Wednesday the 29-year-old announced he would not be competing in what would have been his second Presidents Cup.
"I am announcing my withdrawal from the US Presidents Cup team because of my knee injury," Koepka said in a statement released by the PGA Tour.
"I notified captain Tiger Woods that despite constant medical care and rehab, I am not able to play golf at this time. I consider it to be a high honour to be part of the 2019 team and I regret not being able to compete."
Woods added: "Brooks and I talked and he's disappointed that he won't be able to compete.
"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."
Fowler appeared at the event in 2015 and 2017, winning both times, and is excited to join a 12-man team that features playing captain Woods.
"When I heard Brooks wasn't going to be ready to play, I was bummed for him and the team," he said.
"Then I got a call from both Brooks and Tiger. I was humbled and excited to be given the chance. These team events have been some of the most memorable weeks of my career.
"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 number one but I can assure my team-mates and American golf fans that I will be prepared and ready to do my part to bring home the Presidents Cup."
The USA has beaten its International rivals in each of the last seven editions of the biennial tournament.