Birdies have flown into the cups at TPC Harding Park during the first two hours of the PGA Championship on Thursday.
Before the high-profile groups hit the course, Scottie Scheffler set the pace for the competition with three birdies in his first four holes.
Tony Finau, Jason Day, Daniel Berger and Xander Schauffele were among the golfers to open their respective rounds in red numbers.
Brooks Koepka, Tiger Woods and Justin Thomas are among the previous major championship winners out on course for the morning session.
PGA Championship Leaderboard
Scottie Scheffler (-2)
Brian Harman (-1)
Jason Day (-1)
Xander Schauffele (-1)
Daniel Berger (-1)
Collin Morikawa (-1)
Eight other golfers (-1)
Scores as of 11:45 a.m. ET. Full leaderboard can be found on PGATour.com.
Scheffler took advantage of the first four holes on the back nine to become the first player to reach three under.
The 24-year-old, who was the low amateur at the 2017 U.S. Open, reeled off back-to-back birdies at Nos. 10 and 11 and moved further up into the red with a birdie at No. 13.
After that fantastic start, Scheffler moved back to the pack with a bogey at the 14th hole. Since he was in the first group off the 10th tee, the Dallas native could be the early leader in the clubhouse if he remains under par.
Finau experienced a similar early fate to Scheffler, as he took advantage of his first two holes with a pair of birdies, but he also dropped a stroke on his fourth hole.
The Salt Lake City native's approach at No. 13 found the left green-side bunker and he missed a long par putt to remain at two under.
A handful of other players made an early push into the red numbers, including Berger, Schauffele and Collin Morikawa.
Gary Woodland was only one of the three players in the featured group of 2019 major winners to begin his round with a birdie.
The reigning U.S. Open champion holed a short putt for birdie after leaving a long eagle putt short of the cup.
Woods, Thomas and McIlroy began their round at 11:33 a.m. ET off the 10th tee, which is where the lower scores have been in the first two hours of play.