Seamus Power holds a one-shot lead heading into the second day of the St Jude Classic in Memphis.
Padraig Harrington is two-under and tied for 23rd after dropping shots on the 17th and 18th, while Share Lowry is two-over par.
The Waterford native, who represented Ireland at the 2016 Olympics, lies on five-under par.
Power started off with a birdie on the first, then had a birdie-bogey-birdie run to go two-under at the turn.
Three further birdies on the back nine saw him complete the round in a five-under 65, one shot ahead of a chasing pack of 11 players including Phil Mickelson and the reigning US Open champion Brooks Koepka.
Koepka - who will look to defend his title at Shinnecock Hills, New York, next week - made four birdies in a row in a round of 66 to sit alongside Phil Mickelson, Chris Kirk and Wesley Bryan.
2016 US Open Champion Dustin Johnson is among the pack on three-under.