The 29-year-old wound up tied for fourth at nine under - seven shots off the lead - at Royal Portrush after another frustrating day with the putter on Northern Ireland's north coast.
The muscular Florida native lamented his wayward green work in reviewing Saturday's four under - but insisted his long game has been so sharp that in inclement weather he could yet prevail.
Shane Lowry sits four shots clear at 16 under heading into the final day, with Koepka referencing the Irishman blowing a similar situation at the 2016 US Open.
Koepka almost blew a seven-stroke lead of his own at this year's US PGA at Bethpage, but held on in a gale, and is now eyeing yet more silverware.
"The last time Shane had the lead at Oakmont we saw that," said Koepka.
"In links golf all of a sudden a couple of bad bounces and you never know or in a couple of bunkers.
"And at Bethpage it went very quickly. Bad weather happened at Bethpage. I guess maybe the last, what, 15 holes was very, very windy, especially that back nine.
"Nobody has hit it better than me this week, I've hit it as good as I could possibly imagine.
"I putted the worst in the entire field, if you look at strokes gained. It's been really bad; very frustrating, disappointed.
"But thankfully it's going to blow tomorrow to have any sort of chance. I need it. I need it being, what, seven back.
"Here you need some wind, you need some rain. You need anything that can kind of go your way.
"And that's got to be an advantage. Especially the way I'm striking the ball, I've struck it so good.
"If it's going to be windy, you need to be able to strike it good, control your flight, and figure out where you want the ball to end up.
"If it's going to blow 30, it can get out of control very quickly. I need to figure out the putter. I think there's some weeks where you just don't make anything.
"They feel like good putts when they come off the blade, but they're burning the edge, that's the only thing I can say. They feel like good putts, they're all tap-ins right there."
Koepka could become the first man to complete a top-two finish in all four majors in a calendar year this weekend, but he remains solely focused on victory.
Asked if his fine majors record could have his rivals looking over their shoulders, he said: "It doesn't matter to me, I'm looking at the top spot, that's it, that's the only thing I'm looking at.
"It doesn't matter. I'm assuming they probably do. But at the same time I have no idea, I've never asked anybody.
"I can only look at this as being seven back. It's just not the week that I've expected, but at the same time there's one more round, so I need to figure it out."
