Former US Open champion Justin Rose was frustrated not to make the most of a brilliant start as low scoring looked to be the order of the day in the 96th US PGA Championship at Valhalla.
The world number five raced to the turn in just 31 at a venue where he made his Ryder Cup debut in 2008 and finished with three points from four matches, but after picking up another shot on the 13th the 34-year-old's charge was halted with bogeys on the 15th and 16th.
Rose, who won back-to-back events for the first time in his career in the Quicken Loans National and Scottish Open recently, birdied the 18th to complete a 67 and finish four under, one behind clubhouse leaders Marc Warren and Brooks Koepka.
"I had it going, five under through 13, so I was looking to get it to maybe seven or eight under for the round and who knows where that would put me going into tomorrow," a disappointed Rose said.
"I would say the winning score is going to be 16 under, somewhere in that realm. When you start even par you've got to go all guns blazing. I felt like I could have got halfway there today, but it wasn't to be.
"Some parts of the golf course are really easy out there," Rose said. "Getting close to the pin with your irons is easy, but that's if you catch a good lie in the fairway. Obviously the fairways are completely saturated right now and the fact that they are so wet probably is a good thing it's not picking up much mud.
"But if it drys out at all it's going to be a nightmare out there tomorrow if we don't get a little rain from now until then. The ball is going to pick up so much mud, which is obviously tough conditions to play in."
England's Danny Willett had also jumped up the leaderboard courtesy of birdies on the second and third and chipping in for an eagle on the fourth, which had been reduced to 292 yards to allow players to try to drive the green.
A birdie on the 10th then took Willett to six under par and just three off the lead held by Rory McIlroy, who had yet to begin his third round.
Joint clubhouse leader Warren was enjoying his second experience of the year's final major after finishing in a tie for 12th on his debut at Oak Hill 12 months ago.
"I played very well again today," said Warren, who finished third behind Rose in the Scottish Open. "I drove it really well so I was able to be aggressive due to the conditions and went at a lot of the flags. I gave myself a lot of chances and holed a few more putts today.
"Hopefully I can do the same again tomorrow and there is no reason why not the way I am playing."
Warren finished his round in style with four birdies in the last five holes, holing from 15 feet on the 16th, 30 feet on the 17th and two-putting the par-five 18th, one of two holes where the pin had been moved to higher ground due to the wet conditions and a forecast for more rain.