US Open champion Martin Kaymer took advantage of benign scoring conditions to grab a two-shot lead over Bubba Watson after the opening round of the four-man PGA Grand Slam of Golf in Bermuda.
After a red-hot start that included three birdies and an eagle in his first seven holes, the German mixed two birdies with a bogey on his back nine for a six-under 65 at the Port Royal Golf Course in Southampton.
"The back nine, that's definitely more challenging than the front nine," said Kaymer, who coasted to his second major win by eight shots at the US Open in June. "The first six, seven holes, they're important that you take advantage of them, that you make at least two or three birdies."
Masters champion Watson carded five birdies but dropped his only stroke of the day at the par-three 16th for a four-under 67 while Rory McIlroy, this year's PGA Championship and British Open winner, was a further two shots back.
The elite 36-hole event is for the winners of the year's four majors.
American Jim Furyk, who received an invitation to the event following a double major season for McIlroy, was seven shots off the pace after returning a one-over-par 72.
The final round will be played on Wednesday.