Martin Kaymer opened with a six under 65 at Port Royal in Bermuda to lead the PGA Grand Slam of Golf by two shots from Bubba Watson (67) with Rory McIlroy four adrift after a 69.
World No 1 McIlroy was briefly in contention at three under through seven holes before back-to-back bogeys at the eighth and ninth killed his run.
On the back nine, the Open and US PGA champion birdied the par-three 13th but bogeyed the par-three 16th before narrowly missing for eagle at the 17th and tapping in for birdie.
"I wasn't 100 percent on, that's for sure," McIlroy said. "I started pretty well, and then the two bogeys on the 8 and 9 sort of took the wind out of my sails a little bit, and I just found it hard to get going after that."
Jim Furyk bogeyed two of the last three holes to finish the day with a one over 72.