AUGUSTA, Ga. (AP) — Bryson DeChambeau was the mad scientist who calculated barometric pressure and the decay of spin rate in altitude when trying to figure out how to best play the game.

Then he became the incredible bulk, adding 40 pounds of muscle and mass with a diet of some 3,500 calories a day in an effort to swing the club faster and hit the ball farther than anyone.

The third iteration he showed at the Masters on Thursday might be the most daunting.

“The golf phase,” DeChambeau said Thursday after opening with a 7-under 65, his best start in a major and lowest score at the Masters. “Trying to be the best golfer I can be.”

DeChambeau was plenty good in a relentless wind, taking a one-shot lead over Scottie Scheffler in the rain-delayed opening round. Scheffler hasn’t changed at all. The world’s No. 1 player was practically flawless from tee to green.

The first round could not be completed because of a 2 1/2-hour delay from overnight rain that drenched Augusta National, leaving the greens softer than they have been all week. The test came from a steady 20 mph wind, with gusts twice that strong.

Among those still on the course was Tiger Woods, who was 1-under par through 13 holes when it was too dark to continue. He next faces 23 holes today, an endurance test for his battered legs, as he tries to set the Masters record by making his 25th consecutive cut.

Nicolai Hojgaard of Denmark, one of 17 newcomers to the Masters, was at 5 under with three holes to play. Max Homa was at 4 under through 13 holes.

DeChambeau put on a clinic of power and putting, always a good recipe at Augusta National.

“I’m just in a place where I’m repeating a motion, trying to do the same thing over and over again,” he said.

He ran off five birdies in a six-hole stretch on the back nine, including a two-putt birdie on the par-5 15th when his risky shot under a pine tree cleared the water fronting the green and left him 40 feet away.

“It clipped the tree. I hit four pine needles rather than five, and it worked out perfectly,” said DeChambeau, not entirely rid of his precise calculations.

Scheffler teed off about two hours later when the wind was at full force, and part of him was surprised to see so many red numbers under par on the large, white boards.

“I’ve played this tournament once before in some pretty high winds, and it’s an extremely challenging golf course,” Scheffler said, giving credit to caddie Ted Scott for “guessing the wind correctly” on a number of shots.

He had the only bogey-free round of the 89 players in the field, no small task on a day like this. Three of his six birdies came on the par 3s, one of those when he holed a bunker shot from behind the 12th green.

DeChambeau feels he got fortunate with his shot that grazed the tree. There was no doubting the break Scheffler got with his second shot on the par-5 13th, when he flinched upon hearing a shot hit from another fairway. Scheffler’s ball came up short, and he assumed it would roll back into the tributary of Rae’s Creek that winds in front of the green.

The turf was soft enough that it stayed up, and he chipped it close to make birdie.

“I’ve never seen a ball stay up there,” Scheffler said. “I don’t know if that will happen again this week. I’m hoping I don’t find out.”

Scheffler began as the 4-1 favorite, according to FanDuel Sportsbook, the shortest odds since Tiger Woods nearly two decades ago.