Bryson DeChambeau carded a fine opening-round 66 to lead the European Open, while Patrick Reed birdied his final two holes to sit four shots back.
Starting at the 10th hole, DeChambeau made four birdies in his opening nine holes and, although a dropped shot at the third stemmed his momentum briefly, a further three gains followed on the way home to leave him six under par.
That was enough to head a tight pack, with French trio Joel Stalter, Romain Wattel and Mike Lorenzo-Vera, and Germany's Benedict Staben all one stroke back.
"It's great to start out with six under par," said DeChambeau. "I think it's one of my lowest rounds on the European Tour so I'm very pleased.
"I haven't been hitting it my best so I'm still working on my game and it's starting to turn into some form. I'm missing in the right places and making some putts which is great. If you do that out here you're going to be up there."
Masters champion Reed struggled for fluency at Green Eagle, a birdie at the first failing to set the tone for a positive round as he stood on the 17th tee six shots behind DeChambeau.
But claiming shots at each of the last two holes put Reed firmly among the chasing pack, his round of 70 leaving the 27-year-old level with Charl Schwartzel, with whom he made up the group of the day along with defending champion Jordan Smith, who shot 71.
Amateur Nicolai Hojgaard was on track to sit on DeChambeau's shoulder but dropped shots on his last two holes left the 17-year-old with a respectable three-under round, the same score as world number 15 Paul Casey.