Tiger Woods shot an error-strewn 75 as Rory McIlroy made a positive start at the first FedEx Cup play-off event.
Woods, playing his first round since missing the cut at the Open last month, ended the first day of the Northern Trust at Liberty National four over par and 13 strokes behind leader Troy Merritt.
McIlroy recovered from a bogey on the 10th, his first hole, to record an eagle and five birdies in a six-under-par 65 that put him in a tie for fifth three shots off the lead.
Americans Tony Finau and Webb Simpson were alongside him while Dustin Johnson was second on eight under with Kevin Kisner and Jon Rahm one back on seven under.
Merritt recorded nine birdies in his flawless 62.
Open champion Shane Lowry returned to play for the first time since his triumph at Portrush last month. He finished on two under-par, although it might have been better but for a double-bogey six on the fifth hole.
Two late bogeys saw Graeme McDowell drop back to level par.
Masters champion Woods, who carded three birdies, five bogeys and a double bogey, did not use the stiff back which forced him to play a limited role in the pre-tournament pro-am as an excuse.
Woods, who could fall outside the world's top 30 if he misses the cut, said: "I knew I had to go get it, post a low one, and didn't do it.
"I'm going to have to figure out a way to get this thing under par and hopefully move on to have a chance on the weekend to keep progressing and keep going lower. I've got to get into the red at the end of the day tomorrow for sure."
McIlroy was pleased with his day's work.
"I played well," the Northern Irishman said. "It was a little bit of a scrappy finish, I had to get up and down twice (for par on the eighth and ninth), but I played better.
"I hit some better iron shots today than I saw all week in Memphis, hit some nice little left-to-right shots that I didn't have a couple of weeks ago and I drove it well, so if I continue to drive it well around here hopefully I'll give myself plenty of chances to make birdies."
McIlroy began the week second in the FedEx Cup standings and played the opening round alongside leader Brooks Koepka and third-placed Matt Kuchar.
The 30-year-old won the overall FedEx Cup title and USD 10million bonus in 2016 and would love to repeat the feat this season, especially with the first prize increased to a staggering USD 15million.
"I really like the play-offs," McIlroy added. "Brooks and Kuch and I were playing together today and that could be the same thing next week depending where we end up in the standings after this week.
"I like that you have that intensity from the start. It was cool to play with those guys and I have another day with them tomorrow, sort of keep an eye on what they're doing and try to play another good round of golf."
The top 70 players in the FedEx Cup after this week advance to the BMW Championship and the top 30 after Medinah qualify for the Tour Championship.
Woods is projected to fall from 28th to 35th in the standings after his first round.