«No,» Koepka said when asked if he had any doubts. «I feel confident. I feel good.»
Scott was seemingly paralysed on moving day.
He started the day seven adrift of Koepka, in a share of second, but finished nine behind after a lacklustre two-over par 72 dropped him to three under.
On a tough day of scoring, Koepka still salvaged an even-par 70 and, at 12 under, leads by seven from world No.1 Dustin Johnson (69), Luke List (69), Thailand’s Jazz Janewattananond (67) and Harold Varner (67).
Koepka has made a mockery of Bethpage Black’s reputation as a brute test, bludgeoning the course with raw power and pinpoint accuracy.
He has averaged 304 yards in driving distance while hitting 61 per cent of fairways. The Florida native also leads the field in greens in regulation, finding 80 per cent with approach shots.
The burly Koepka is gunning for his fourth major victory in less than two years, having won last year’s PGA Championship and the past two US Opens.
Scott said Koepka had moved the goalposts on what was required at majors.
«Driving it in the fairway, at his length, for a whole week is a huge advantage,» Scott said.
«If he can be that driving machine, then maybe he is pushing the boundaries to another level for what has to happen [at majors]. No one can keep up.»
Koepka has only won twice in the US outside the majors.
The 29-year-old has figured out how to treat golf’s four biggest events like any others, and is already assured of a Hall of Fame career.
«I don’t need a sports psychologist. I know what I’m doing,» Koepka said.
«It’s simpler than what guys think. [They] make the mistake of trying to figure out what’s different at a major.
«It’s just about focus, grinding it out and sucking it up.»
Jason Day, the 2015 PGA Champion, shot 69 and was next best of the Australians at two over. Day’s countrymen Cameron Smith (74) and Lucas Herbert (73) are at seven over.