Twice Masters champion Watson used a red-hot outward nine as a springboard en route to a sizzling five-under-par 65 at Plainfield Country Club, setting the pace with fellow Americans Spencer Levin and Tony Finau, and Colombia’s Camilo Villegas.
New Zealander Danny Lee, Americans Jason Dufner, Cameron Tringale and Bryce Molder, and Britons Paul Casey and Russell Knox opened with 66s in the first of the PGA Tour’s four lucrative FedExCup playoff events.
Spieth, however, was let down by his usually stellar short game as he limped to a 74 in his first competitive round since he replaced Rory McIlroy at the top of the rankings by finishing second at the PGA Championship 11 days ago.
“After the tee shots, that is the worst round I’ve played in years,” Masters and U.S. Open champion Spieth, who hit 11 of 14 fairways on a challenging Plainfield layout, told reporters.
“It was really a very unique round for this year. I hit my first 11 fairways today and that’s really hard to do out here.
“Typically when I hit the fairways, I’m not over par. That’s what was weird about the round.”
Spieth covered his front nine in a promising two-under 34 but then ran up five bogeys, a double at the par-three third after his tee shot found water and a lone birdie after the turn.
The best putter in the game recorded two three-putt bogeys as he carded his worst score since a first-round 75 at the Players Championship in May.
Asked how he would respond, the 22-year-old Texan replied: “I do what I have done best, bounce back. I come back tomorrow strong.
“I know I can still shoot a low round if I hit the shots I need to hit … hopefully see a few more putts go in.”
Left-hander Watson, who played with Spieth and PGA Championship winner Jason Day of Australia in a high-profile grouping, surged to the top of the leaderboard with five birdies in his first nine holes.
He picked up two more shots before a poor swing at the par-three sixth and a three-putt at the tricky ninth cost him two bogeys in his last four holes.
“All in all, it’s a good round but the back nine … if I just make a better swing on the par-three and then a two-putt, it’s not too bad,” said Watson.
“I missed the cut the last time I played here so we are ahead of the curve right now,” he grinned.
World number three Day, who withdrew from Wednesday’s pro-am competition due to a back issue, opened with a 68.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)