Brooks Koepka lurched from the sublime to the ridiculous to leave Bryson DeChambeau to set the pace on day two of the 83rd Masters.

Koepka, who is seeking a remarkable fourth major title from his last seven appearances, made an ideal start with a birdie from 10 feet on the first, only to then make a complete mess of the par-five second at Augusta National.

After pulling his tee shot into the trees, Koepka attempted a risky escape rather than pitching out sideways and succeeded only in finding more trouble and was forced to take a penalty drop.

The 28-year-old eventually took his medicine and played out on to the fairway but, after finding the green with his fifth shot, he two-putted from 25 feet for a double-bogey seven.

That left DeChambeau, who had birdied the same hole earlier, at the top of the leaderboard on seven under par, a shot ahead of 48-year-old Phil Mickelson, who is attempting to become the oldest major champion in history.

Koepka was a shot further back after his first dropped shots of the week with Ian Poulter on four under after one birdie and one bogey in his first six holes.

Rory McIlroy had struggled to an opening 73 on Thursday, getting under par for the first time with birdies on the 13th, 15th and 16th, only to bogey the last two holes.

That left the Northern Irishman in a tie for 44th place overnight and needing to defy the odds to win a first green jacket to complete the career grand slam as the last 13 Masters winners all enjoyed a place in the top 10 after the first round.

McIlroy headed straight to the putting green following his round after struggling to read putts on the slower surfaces, saying: "I made five birdies, that wasn't the problem.

"I just made too many mistakes.

"And I'm making mistakes from pretty simple positions, just off the side of the green on 17 and 18 being prime examples of that."

McIlroy faced a long wait to begin his second round in the final group due out at 1400 local time (1900 BST), by which time the size of his task would likely become clear.