Rory McIlroy was stumbling towards a third season without a major title as Jordan Spieth's faint hopes of becoming the youngest player to complete a career grand slam came to an end.
McIlroy came into the US PGA championship as the pre-tournament favourite on the back of top-five finishes in his last two starts and a brilliant record at the host venue Quail Hollow.
The 28-year-old won his first PGA Tour title here in 2010, lost out to Rickie Fowler in a play-off in 2012 and stormed to a seven-shot victory in 2015, which included a course record of 61 in round three.
However, changes to several holes and a switch to bermuda rough and greens had not suited the four-time major winner, whose last major title came in the 2014 US PGA at Valhalla.
No player has ever won the final major of the year after trailing by more than nine strokes after 36 holes, with McIlroy 10 adrift of Hideki Matsuyama and Kevin Kisner after two rounds of 72.
And the Irishman never threatened to buck that trend as he fell further down the leaderboard thanks to four bogeys and two birdies in the first 13 holes of his third round.
Open champion Jordan Spieth had already completed a 71 to remain three over, the 24-year-old dropping three shots in the first seven holes before stopping the rot with birdies on the eighth and ninth.
A hat-trick of birdies from the 14th briefly raised the prospect of Spieth getting back into contention, but the world number two found the water with his approach to the 18th to run up a double-bogey six.
"Obviously any week you don't have a chance to win, you've fallen short of where you would like to be," Spieth said. "Disappointing would have been going home after two days. I think I saw some highlights today.
"Like Michael (Greller, his caddie) was saying, we could break the season into quarters. This is the start of the fourth quarter. At the US Open on Sunday I was out of it, but I gathered a little something off that Sunday round that led to two wins in two tournaments after that, including a major.
"Just one round like that can do that. That's what I'm looking to do here.
"My goal was to try to work our way into a back-door top 10. The last kind of stinks because it sets me back there - 18 is just a ridiculously hard hole today."
At the top of the leaderboard, seven pars and a birdie were enough to give Kisner a one-shot lead over fellow American Chris Stroud and Matsuyama, who had bogeyed the first but matched Kisner's birdie on the par-five seventh.
Stroud, who was one of 25 players to complete their second rounds on Saturday morning after Friday's weather delay, had carded three birdies and a bogey in his first eight holes.
Australia's Jason Day was two shots off the lead on six under, with Louis Oosthuizen a shot behind despite needing treatment and strapping on his right arm after jarring it when playing a brilliant escape shot from the base of a tree on the second hole.
Day had been one of the players to benefit from a scramble to finish in near-darkness on Friday evening, with playing partner and world number one Dustin Johnson running to the 18th to tee off and ensure his whole group could finish.
''That's the biggest or most clutch thing I've ever seen anyone do for me,'' Day said. ''I had to give him a hug for it. He was happy as well obviously, to be able to finish and not have to wake up at 5.30.''
For the second successive major the cut fell at five over par, with 75 players qualifying for the final two rounds.
Austria's Bernd Wiesberger would have made the cut four over par with a birdie on his final hole, but bogeyed it instead to miss out by a shot and end his streak of 26 consecutive events earning world ranking points.