Jordan Spieth had a post-Masters letdown Thursday, shooting a 3-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 that Spieth was not at his Augusta National best.

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 were at 5-under 66.

Spieth chalked it up to a bad day of golf. He'll need significant improvement Friday to make his eighth consecutive cut.