He counted himself out after signing for a 66 yet Australian Adam Scott will start the final round just four shots off the lead at The Open Championship at Royal Troon.

As 36-hole leader Shane Lowry came back to the fold with back-nine struggles on his way to a 6-over 77, those out early cashed in on the benign conditions to rocket up the leaderboard.

Scott was among those, climbing an astonishing 44 places with a round of 5-under 66 to be in a tie for 10th at even par.

American Billy Horschel (69) made bogey and English qualifier Daniel Brown (73) double-bogey on the final hole to make the margin manageable, Horschel the outright leader through 54 holes at 4-under.

It was a margin Scott had assumed would be insurmountable when he finished hours earlier.

“I’m probably not going to be in the mix, let’s be honest,” was the 2013 Masters champion’s honest appraisal. “I’m likely seven to nine shots behind, I would guess.

“If I am, then that’s a bonus, but I’m going to need wind and everything to be in my favour to kind of be in the mix.

“You can’t really complain about 66, but when you’re so far back, you kind of need everyone possible.

“I think I got what I deserved out there. I played some fairly good golf and didn’t make too many errors.”

Two birdies out of the blocks was the ideal start for Scott as Royal Troon provided a window for the early groups to make an impression on the leaderboard.

He made a two at the par-3 fifth and a fourth front-nine birdie at the par-4 seventh to go out in 4-under 32.

His lone bogey at 15 was wedged between birdies at 14 and 16 as rain made conditions challenging for the later groups.

Runner-up a week ago at the Genesis Scottish Open and runner-up at Royal Lytham in 2012, Scott earned himself a Sunday sleep-in with the knowledge that his best golf in the final round might be enough to win the Claret Jug.

“To win golf tournaments, not many guys are winning not playing very well,” said the 44-year-old.

“To beat all these players, you have to be there, and a few guys every week are on doing that. The rest are making up the numbers.”

Tied for seventh at the halfway mark, Jason Day was one of many players to struggle in the rainy afternoon.

While fellow Queenslander Scott started with two birdies, Day began his day with two bogeys but birdied the par-5 fourth and the treacherous ‘Postage Stamp’ eighth to be even par through nine.

But, like so many around him, the back nine bit hard as Day came home in 5-over 40 for a round of 5-over 76 and tie for 33rd.

There were mixed fortunes, too, for the two Kiwis who made the cut, Daniel Hillier (68) climbing 39 spots and into a tie for 15th as Ryan Fox (76) dropped into a tie for 70th.