European Tour Members Kiradech Aphibarnrat and Henrik Stenson were the early pacesetters as the first round of the WGC-Bridgestone Invitational began in Ohio.
Thai Aphibarnrat, who claimed his maiden European Tour title at the Maybank Malaysian Open earlier this year, recovered from an early bogey at the 13th with four birdies to reach three under at Firestone Country Club.
He joined Swede Stenson on that mark after the former Ryder Cup star made an electric start with a birdie on the first and eagle three at the long second to turn in 32.
American trio Ryan Moore, Jason Dufner and Webb Simpson were all one behind in the early stages, with Italian Matteo Manassero part of the group on one under par.
