Defending champion Tiger Woods, playing with his old driver in the bag, tripped out of the gate with a bogey at the 10th, his first, but countered a few holes later with a birdie at the 12th.
Woods added a birdie at the 16th to make the turn at 1-under but found trouble again with a bogey at the first.
The 27-year-old, who is finalizing his preparation to make a run at the PGA Championship in two weeks, picked his game up down the stretch with a birdie at the fourth and back-to-back birdies starting at the sixth en route to a round of 3-under-par 69.
'I wasn't comfortable today with my swing,' said Woods. 'I know what I need to do, it's just a matter of getting enough trust in doing it.'
Sposa, who has missed the cut in each of his previous four appearances at this event, notched a birdie at the second to start his round but had nothing but pars the rest of the way on the outward nine.
Things changed quickly for the former University of Tennessee star and he hit a wedge to 12 feet for a birdie at the 10th. At the par-4 12th, Sposa hit his approach from 110 yards out and watched as it rolled into the cup for an eagle.
Sposa kept the run going with a pair of birdies from the 13th to move to minus-6 and found a greenside bunker in two at the par-5 16th.
The 34-year-old blasted out of the sand to six feet and drained the putt to secure sole possession of first after the opening round.
'It was a very good day,' said Sposa. 'I have never played good here. I've been here five years. I just can't putt these greens. You know, for the first time ever, I felt good over the putter on these greens, had the speed, had the line. I really felt like I could make any putt I got.'
Sposa last found himself at the top of a leaderboard after the first round of a PGA Tour event when he shared the lead after 18 holes of the Texas Open in 2000.
'Obviously, I'm not thinking about winning this golf tournament,' said Sposa. 'I'm thinking about going out and playing a solid round again tomorrow.'
Perks, who broke through with a victory at last year's Players Championship, hasn't done much in 2003, with his best finish a tie for 13th at the Buick Invitational.
The New Zealander started on the 10th and torched the back nine at Warwick Hills. Perks ran off four consecutive birdies starting at the par-3 11th and added back-to-back birdies from the 16th to make the turn at 6-under.
After the hot start, Perks cooled off and played the front side at even-par to finish one shot off the lead.
'I was so hard on myself, expecting to play well every single week,' said Perks. 'You've just got to be patient. Just because we come out of nowhere and win, you shouldn't expect yourself to win every week.'
Stuart Appleby posted a 5-under 67 to finish two shots off the lead along with Shaun Micheel, Thomas Levet, Neal Lancaster, Kent Jones, Chris DiMarco, Garrett Willis, Heath Slocum, Hunter Mahan and Jason Buha.
One player who now finds himself in the spotlight made his return to the tour after becoming the upset winner of the British Open two weeks ago at Royal St. George's.
Ben Curtis, who pulled out of last week's Greater Hartford Open to adjust to his newfound status, started on the 10th and tallied three birdies over his first nine holes. He added two birdies and a bogey on the front side to finish at 4-under-par 68.
Curtis was joined by U.S. Open champion Jim Furyk, Tom Byrum, Fred Funk, Rocco Mediate, Darron Stiles, Grant Waite, Paul Goydos, Robert Damron, Spike McRoy, Greg Reynolds and John Daly in a tie for 16th.