Former US Open champion Graeme McDowell of Northern Ireland withdrew from the US PGA Tour's Travelers Championship on Wednesday after his caddie, Ken Comboy, tested positive for COVID-19.

McDowell, a February winner at the Saudi International on the European Tour, told Golfweek late Tuesday that he planned to get tested and fly home to Florida. "For the protection of the field and for my own physical and mental well-being, I'm going to take a test tomorrow morning then jump on a private plane," McDowell said. "I'm going to get myself out of here, home to Florida and decide whether I need to quarantine myself from my family."

Comboy took a commercial flight from Texas to Florida two weeks ago after the PGA's first comeback event following a three-month coronavirus shutdown when McDowell's private plane proved too small for his group, according to Golfweek. McDowell tested negative for COVID-19 on Monday and played a Travelers practice round Tuesday with Shane Lowry and Brooks and Chase Koepka before Comboy tested positive Tuesday.

The 40-year-old from Northern Ireland who won the 2010 US Open became the third player to withdraw from the event. South Carolina and Cameron Champ withdrew Tuesday after testing positive. Both US golfers are isolating under tour guidelines.

"I feel great physically and I was obviously surprised and disappointed to learn of the test result," Champ said. "It's important now to take the necessary steps and measures to protect others, including my loved ones."

World number six Dustin Johnson, the 2016 US Open champion, says he is pleased with the testing program and safeguards the PGA has in place. "The tour is doing a great job with all the things they have, the precautions we have to take," Johnson said. "For the most part, most of the guys are pretty safe and they are doing a great job."