Jordan Spieth had a post-Masters let down on Thursday, shooting a three-over 74 at the RBC Heritage to end his run of 16 straight rounds under par.

Spieth vowed his whirlwind, two-day celebration tour of New York after winning the green jacket Sunday wouldn’t affect his focus.

But it was apparent early on at Harbour Town Spieth was not at his Augusta National best.

“Got a good feeling about tomorrow,” Spieth said.

“Feel like I got some swings in, got in somewhat of a rhythm and can at least go out and feel the shots. It was just an off day and it happens.”

Spieth was visibly frustrated on the eighth hole when his second shot from pine straw landed well short of the green.

The 21-year-old Texan was eight shots behind leaders Graeme McDowell and Matt Every, who finished at five-under-par 66.

Spieth chalked it up to a bad day of golf.

He’ll need significant improvement on Friday to make his eighth consecutive cut.

Cameron Smith is tied fourth after firing a three-under-par round to be the best-placed Australian.