Charl Schwartzel of South Africa holds the lead after the opening round of the Memorial Tournament at Muirfield Village in Ohio.
Schwartzel shot a superb seven-under-par round of 65 and is one clear of American Scott Piercy, who carded a 66.
England's Justin Rose is five shots off the pace after opening with a 70 and Tiger Woods is a shot further back, while Rory McIlroy was not on song and will do well to make the cut after a six-over total of 78.
Schwartzel played the back nine first and powered up the leaderboard with four birdies in a row from the 14th.
He reached eight-under with another four-birdie burst from the fourth but then made a double-bogey at the par-three eighth.
However, he picked up a 10th birdie of the day at the ninth to finish just in front of Piercy, with Josh Teater, Russell Henley, Kyle Stanley and Charlie Wi a shot further back after they recorded 67s.
Schwartzel said: "That was one of the best rounds of the year, I hit the ball beautifully.
"I shot it so well and I gave myself so many chances."
Rose played the back nine first and started with a bogey at 10, but that was his only dropped shot of a steady day and birdies at 14, two and seven mean he is in a tie for 14th.
Woods was one-under through the turn and, having birdied 11, he gave the shot back immediately with a bogey on 12.
He then birdied 14 but ran up a six on the par-five 15th and, having reached two-under again with a birdie at 17, he finished the day with a bogey to drop back once more.
Woods said: "It was probably the highest score I could have shot today.
"I didn't make much. Hopefully tomorrow I can make a few more putts.
"The greens were a little bit tough this afternoon, a little crusty and a little bumpy. I don't think there were too many low scores this afternoon."
China's Guan Tianlang, who at 14 became the youngest player to make the cut in a major at the Masters last month, bogeyed two of his last three holes for a 72.
Lee Westwood returned a 76, while Sweden's Robert Karlsson is nicely placed after an opening round of 69.