Simon Khan, winner of one PGA title already this season, put himself in the hunt for another in Wisconsin.
The Englishman, who the BMW PGA Championship at Wentworth Club in May, was the joint leader at the US PGA Championship until he bogeyed the last three holes of his second round.
The 38 year old had to cram 29 holes - more than any other player in contention - into a day that began with another long fog delay, so mental fatigue may well have had something to do with his finish on the demanding Whistling Straits course.
It handed Matt Kuchar a one stroke overnight advantage over fellow American Nick Watney - and lifted 21 year old Ulsterman Rory McIlroy and 19 year old Korean Noh Seung-yul up into a tie for third along with a group including Khan on five under par, three behind.
As for Tiger Woods, he had to wait until nearly 6pm to get back on the course and after five opening pars - many of them hard work - remained one under.
With play being called off just before 7.30pm local time, he and 77 others will complete their rounds in the morning - fog, of course, permitting.
"On the whole it was really a good day," said Khan. "My driver cracked this morning after one hole. I hit my tee shot on 18 when we restarted and the face cracked.
"So I pulled out my replacement driver, but I haven't hit it before and I struggled with it, to be honest.
"Then the wind this afternoon started really getting up and stayed pretty constant - the course really showed teeth.
"Saying that, you still got birdie opportunities and you just got to play the hard holes well."
Khan knew he was playing in the final Major of the year only at the start of last week, but such short notice was never going to bother him - he was not in the BMW PGA Championship at Wentworth until just a few days before.
Last year's Qualifying School winner stood 474th in the world entering that week, but he is now 107th - three places higher than Korean Y E Yang was when he won this title by beating Woods down the stretch 12 months ago.
So it could be a big weekend ahead for a man who feared for his future less than nine months ago and his experience from Wentworth will only help.
“What I learnt from Wentworth was it was more about what I had to do on the course,” he said. “What I managed to do at Wentworth was forget about who was one the course and what the field was like. It doesn’t matter.
"The test is the golf course, every week it is. I managed to go out and play a final round and really stick to my plan and what I was trying to do. That’s what pleased me most, almost more than the result. That’s what I will be concentrating on this weekend and if I do that I will be happy.”
McIlroy had been three over par after four holes of his first round on Thursday, but he battled back for an opening 71 and then added a 68.
Third at The Open Championship last month and in this event last year, he said: "I'm in a great position and I can just go out and play some good positive golf. I like the position I'm in."
Phil Mickelson was in on two under after a 69, while among those on level par was Steve Stricker, who also came into the week with a chance of unseating Woods as World Number One.
Kuchar is currently seventh in the American Ryder Cup standings - and, unlike the Europeans, this is their final counting event.
With scores of 67 and 69 he certainly impressed playing partner and European Captain Colin Montgomerie.
But with so much of the second round still to come - and much of it in the morning, fog permitting - Kuchar wisely downplayed his position.
"I think we'll just wait and see," he said. "They (the later men) could get lucky.
"This morning wasn't pleasant to wake up at four after getting back to the hotel at nine last night.
"I don't feel great on five hours' sleep. My body just feels funny."
Darren Clarke was the European who at the start of the day was best placed to challenge, three under with five holes of his first round to come.
Instead he had three bogeys and then a double bogey straightaway for a 74, but battled back to level par with a 70.
Noh – winner of the Maybank Malaysian Open earlier this year – revealed a famous compatriot had given him something of a heads up this week.
“When I was playing the practice round with K J Choi he told him about the golf course, how to play like here and there or something and that is how I played well,” he revealed after a 71.
Those out on the course who will resume their second rounds at 7am local time include Francesco Molinari at four under par through five holes.