American Matt Kuchar returned to Whistling Straits to complete a five under par 67 and claim the lead after the first round of the US PGA Championship.
The 32 year old, with two US PGA Tour titles to his name, eagled the par four 13th in a round that also contained four birdies and a bogey.
Four players were in the clubhouse tied for second - South Africa's Ernie Els and 19 year old Korean Noh Seung-yul joining overnight clubhouse leaders Bubba Watson and Francesco Molinari on four under.
"I am so happy," said Noh, who became the second youngest winner on The European Tour with his Maybank Malaysian Open victory this year.
"I have come here as an invite and I want to play as well as I can. It is a top class event.
"It is a very big event for me. I won the Malaysian Open and that has given me a lot of confidence. I want to follow KJ Choi and have done well this season. I have had a lot of good finishes this year and that gives me confidence to do well. This is a very tough course though."
Els said: “I really like the course. It doesn't play like a links as we know, but it's just got a great look to it. I'm reading the greens quite well, so we'll see how it goes this time.”
Nick Watney and Angel Cabrera were also on four under with two holes of their first round remaining, while Gonzalo Fernandez-Castaño birdied the first two holes of his second round to move into a tie for second.
Kuchar birdied the long second and for a while led by two, but he then bogeyed the sixth and he was joined on five under compatriots Zach Johnson and DA Points and also by 19 year old Korean Noh.
Fernandez-Castaño was two behind after turning in 35, while Rory McIlroy made two threes to take up a handy position on three under.
Simon Khan, who had less than ten minutes before teeing off again, hit a superb tee shot to within three feet of the flag on the short third and the putt made him four under again.
That was only one behind American quartet Kuchar, Dustin Johnson, Bryce Molder and Nick Watney, who reached six under before bogeying the difficult 15th.
McIlroy was up into a tie for 11th at three under and Clarke took his revenge on the 17th with a third birdie of the round to be level par.
