Bo Van Pelt and Hideki Matsuyama both carded a first-round 64 to earn a share of the lead after day one of the Memorial Tournament in Dublin, Ohio.
Van Pelt holed no fewer than 10 birdies, along with two bogeys, to finish the day on eight-under-par and level with Matsuyama, who enjoyed a bogey-free round.
The duo looked like being joined at the summit by Jason Dufner, whose two eagles had put him level with the pair going into the last.
However, a double-bogey on 18 saw Dufner finish on six-under and level with Scotland's Russell Knox, who picked up seven birdies.
Former world number one and five-time Memorial winner Tiger Woods endured a rollercoaster return to action after a month-long absence.
Four bogeys and a double-bogey saw Woods - who started on the 10th - suffer a dreadful front nine, but a less eventful back nine, with three birdies, helped him salvage a one-over-par 73.
Shane Callaghan
