While the world's top 64 players are taking part in the Accenture Match Play Championship in Arizona, a surprisingly strong field has gathered at the Greg Norman-designed El Camaleon course.
John Daly, despite a double bogey, shot a 65, while Norman, playing for the second time this season and just the second time in three years, fired a 70.
Defending champion Fred Funk, who last year became the oldest winner on the PGA Tour since 1975, stumbled to a 73.
Merrick's score equaled the lowest of his career, which was shot in the first round of this tournament last year.
"I felt like today was more of a solid round than the one last year," Merrick said. "I hit a lot of greens and a lot of good shots, and even missed some more potential birdies."
Merrick faded to a tie for 48th place after opening with the lead in 2007.