Seamus Power heads the Irish challenge at The Northern Trust, seven shots off the lead jointly held by Jon Rahm and Justin Thomas, with the Co Waterford golfer one clear of Rory McIlroy and Shane Lowry after the opening round.
Power carded a one-under 70 around the Liberty National course in New Jersey, with a solid opening nine that featured a birdie on the 13th, before another on the seventh which made up for a bogey on the first.
McIlroy also teed off early with the world number 15 enduring a mixed round. Two birdies and three bogeys on the front nine were balanced out by three birdies, including on 16 and 17, and two bogeys on the back nine as he signed off for a level-par 71.
Lowry was among the late starters and did not enjoy the most ideal of starts as he double-bogeyed his opening hole on the 10th.
Another bogey on 12 dropped the Offaly man down to three over but he rallied with birdies on 13 and 17.
A bogey on the second presented a temporary setback but Lowry finished his round strongly with three birdies and a single bogey in his final seven holes as he joined McIlroy in carding a 71.
But it's fellow major winners Rahm and Thomas who set the pace and lead the way after the opening round as both carded impressive eight-under 63s to move three shots clear of Harold Varner III who is third on five under.
Adam Scott and Tony Finau are part of a six-way tie for fourth, one shot further back on four under.
The second round gets underway on Friday with Lowry teeing off early at 12.31pm Irish time.
Power and McIlroy will get their second rounds underway at 5.11pm and 5.55pm respectively.