Day, who started the day nine shots behind leader Phil Mickelson, was supposed to tee off alongside Rafa Cabrera Bello and Roger Sloan at 8:09 a.m. ET. Instead, Day's tee time was pushed until 9:15 a.m. out of precaution and to give him more time to get test results. He started on the 10th tee and played alone.
After Day started his round, the PGA Tour said in a statement that he had tested negative for COVID-19.
If his test had come back positive, per PGA Tour procedures, he would have been removed from the golf course midround and put into isolation.
Day carded a 69 on Saturday and he's 13 shots behind leader Brendon Todd entering the final round.
The PGA Tour has had seven withdrawals this week related to the coronavirus. Players Cameron Champ and Denny McCarthy both tested positive. Bud Cauley, who played with McCarthy during Thursday's opening round, opted to withdraw before Friday's second round out of precaution, despite a negative test.
The caddies for Brooks Koepka and Graeme McDowell both tested positive, leading to each player's withdrawal. Chase Koepka, Brooks' brother who earned a spot in the field through a Monday qualifier, also pulled out of the event for precautionary reasons because he was in close proximity to his brother's caddie, Ricky Elliott. Webb Simpson also withdrew before the event began after finding out a family member had tested positive for the virus.
The tour said in its statement that all follow-up tests from potential contact with McCarthy were negative.
On Wednesday, PGA Tour commissioner Jay Monahan announced stricter protocols for the safety of all involved, and also to allow golf to continue forward, uninterrupted. He announced additional testing and broadened the scope of those who would get tested, including player instructors. He promised "severe repercussions" to anyone who did not follow the protocols.
"It's pretty clear that this virus isn't going anywhere," Monahan said.
"But everybody knows and needs to know that our future, our ability to sustain this business and to impact the communities where we play and to create so many jobs is contingent on our ability to follow those protocols. So when we have instances where someone hasn't, they will be dealt with. And as I said, the consequences will be significant."