MIAMI • Dustin Johnson is unfamiliar with the course at the Valspar Championship, having not played at Innisbrook for nearly a decade since a missed cut in 2010.
On Thursday, the American world No. 1 finished three strokes back of the leaders in the opening round but was satisfied with his display.
"I played a little better than my score," said Johnson, who carded a two-under 69.
"First time being here in a while, not really used to the golf course. I felt like I hit the ball really well, even hit good putts, just a couple misreads. But, all in all, it was a good score and I felt like the conditions; they were tricky."
Austria's Sepp Straka took advantage of a depleted field, firing a bogey free five-under 66 to seize a share of the first-round lead with Joel Dahmen.
Straka, who is chasing his first win on the US PGA Tour, finished with five birdies at the Innisbrook Golf and Spa resort in Florida.
A number of top players took the week off following the prestigious Players Championship won by Rory McIlroy, but the event still includes Johnson, Jason Day, Patrick Reed and Bubba Watson.
Russell Knox, Kevin Kisner and Luke Donald were tied for third on four under and American Keegan Bradley is part of a five-player group on three under.
Johnson, Watson and Jim Furyk are tied for 11th but are still well within striking distance.
Like Straka, American Dahmen has yet to win on the Tour. He rolled in six birdies and just one bogey. He is coming off a tie for 12th at The Players.
The 31-year-old already had a top-10 finish this season when he tied for ninth at the Farmers two months ago.
Straka's best finish of the season was a tie for 13th at the same event.
Knox had one of the more entertaining rounds by making an albatross on the par-five 11th, after taking a double bogey two holes earlier.
"It's a good way to go from plus two to minus one very quickly," Knox said. "Didn't even have to putt, which was great."
Defending champion Paul Casey opened with a 70, while Jon Rahm made his tournament debut with an even-par 71.
Early tee times did not help Reed, who had a 77, or Day at 74.