Goosen was joined by Billy Andrade, Bob Burns, Aaron Barber, Brad Lardon and Jay Williamson in a tie for second at 4-under-par 68.
'Today was one of the better swinging rounds I've had where I was consistent with my iron play and had a lot of really good shots at the hole,' said DiMarco, a three-time winner on the PGA Tour. 'I was very much in control of my game.'
DiMarco, who has posted three top-10 finishes so far this year, got things started at the TPC at Sugarloaf with a birdie at the fifth. He then hit a sand wedge to four feet for a birdie at the par-5 sixth.
The 34-year-old birdied the par-4 ninth and converted a six-foot putt for a birdie at the par-5 10th. At the par-4 14th, DiMarco drained a 15-foot putt for a birdie and followed that up with a 20-footer for a birdie at the next hole.
DiMarco, who finished in a tie for 23rd at this event last year, stumbled with a bogey at the 17th but managed to hang on to the clubhouse lead as players start to ready themselves for the for the first major of 2003, the Masters, next week at Augusta National.
'It was definitely tough out there. The course isn't playing that long but the greens are like rocks,' said DiMarco. 'I like this course especially when it plays like this. I think it plays better fast and hard. There's some really hard holes out here.'
Goosen opened with a birdie at the first but stumbled with a bogey at the very next hole. The South African made the turn at even-par, but caught fire on the back side.
He birdied the 10th and two-putted for a birdie at the 13th. At the 16th, Goosen hit a 6-iron to six feet for a birdie and drained a five-foot putt at the 17th to finish one shot off the lead.
'I obviously feel pretty comfortable around this course. I like the way it sets up for me, and I like the greens,' said Goosen. 'Although it's playing shorter and the fairways are running. The greens are much more difficult to get close to the flags.'
Rookie John Morgan held a share of the lead with DiMarco, but found trouble at the ninth, his last, with a double bogey.
The young Englishman was joined by Fred Couples, Lee Janzen, Paul Stankowski, Mark Calcavecchia, Paul Azinger and Joey Sindelar in a tie for eighth at 3-under-par 69.
'We all know you have to putt well out here to score well,' said Stankowski. 'You've got to hit good shots. You can't just hit it all over the lot here.'
J.J. Henry, Mike Heinen, Bob Tway, Brandt Jobe, John Huston, Tom Pernice Jr. and Olin Browne finished three shots off the lead at 2-under-par 70.
Phil Mickelson, who is making his first start since the birth of his third child, had four birdies, three bogeys and a double bogey to finish in a tie for 57th at 1-over-par 73.