Scottie Scheffler made a strong start to his defence of the British Open to sit just one off the clubhouse lead of four under par after his opening front nine at Royal Birkdale.
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Scheffler is two shots back after failing to make the most of a fast start under glorious sunshine and scorching temperatures in England's northwest coast.
After his record of 78 successive cuts made dating back four years came to an end at last week's Scottish Open, the world No 1 looked refreshed with four birdies in five holes between the second and the sixth.
But bogeys at the seventh and par-five 17th dropped him back and a birdie putt at the last came to a halt just inches shy of the hole.
"I got off to a hot start in the round today and wasn't able to make as many birdies as I would have hoped to down the stretch," said Scheffler, who has not won on the PGA Tour since January.
"If I continue to strike the ball the way I did today and just keep giving myself looks, that's part of it. Golf is played over 72 holes, and I definitely liked what I saw today."
DeChambeau is set to snap his unwanted streak of failing to make the cut at the previous three majors this year.
The two-time US Open champion has often struggled in the wind of links conditions at the British Open but, with the weather set fair for the next three days, he is hoping to take advantage.
"There's still a lot of golf to be played, but, ultimately from my perspective, I was really excited about the way I played," said DeChambeau.
MCILROY'S SLOW START
England's Daniel Brown and South Korean Im Sung-jae set the clubhouse lead at four under.
The world number 136, Brown, also topped the leaderboard after the opening round at Royal Troon two years ago.
Scotland's Robert MacIntyre is among the chasing pack one off the lead after an encouraging round of 67.
The world number 15 has never won a major but has finished in the top 10 at the British Open three times in six attempts.
"If I won an Open, won any major, if something happened, I could happily walk away from the game of golf," said MacIntrye.
"It would be all my goals that I ever dreamed of complete if I did that, but there's a long way to go."
Tommy Fleetwood is also looking to end his wait for a major win in his hometown of Southport and battled to one under par thanks to two birdies in the final four holes.
"To say that this one wouldn't have extra meaning would be silly because obviously it does," said the world No 9.
"I would have loved to have felt a little bit more comfortable with my swing. I was battling something there. But I loved playing out there."
Rory McIlroy was among the late starters in the afternoon's marquee group alongside 2024 winner Xander Schauffele and world No 3 Matt Fitzpatrick
The six-time major champion got off to a poor start as bogeys at two par threes dropped the Northern Irishman to two over for his opening seven holes.