Davis Love III, Lucas Glover and Billy Andrade are knotted in fifth place at minus-3.
The difficult Quail Hollow layout proved tricky once again on Thursday, with just 32 of the 155 players who teed off breaking par. There are 15 players within two of the four leaders.
Furyk, who lost in a playoff to Vijay Singh last year, started his opening round on the back nine at Quail Hollow. He tallied birdies at the 10th and 18th holes, but the 2003 U.S. Open champion surged up the leaderboard with his play on the front nine.
He birdied the third and fifth holes to get to 4 under, but was one behind Sabbatini at the time. Furyk drained a 10-footer for birdie at the eighth to join Sabbatini at minus-5.
The par-4 ninth proved to be trouble for Furyk, the seventh-ranked golfer in the world. Sabbatini bogeyed the hole before Furyk, who then drove into a right fairway bunker. His approach landed in a greenside trap and the best he could do was blast out to 24 feet. Furyk's par try missed, but he tapped in for a bogey and a share of the lead.
'I'll take it either way. It's 68. I think that's pretty interesting,' said Furyk. ' It's a very good, difficult golf course. It's demanding, and you really have to pretty much have all aspects of your game in good shape to play well here.'
Sabbatini, who is fifth on the PGA TOUR money list, mixed four birdies and two bogeys on his opening nine, the back side at Quail Hollow. He was the first player to reach 5 under par with birdies at two, five and seven, but problems were ahead.
At the ninth, Sabbatini drove into the trees and could not reach the green with his second shot. He hit a solid third shot 11 feet past the flag, but the South African missed the putt to fall into the logjam.
'Three weeks off so I was a little rusty out there today but managed to hang in there and played pretty solid golf the whole way,' said Sabbatini. 'I limited my mistakes to a severe minimum.'
Immelman, a South African, began on the back nine, and tallied two bogeys and two birdies. His biggest problem came at the par-4 14th when he drove in the rough, then his approach hopped into the water. Immelman made double bogey to make the turn at 2-over-par 38.
The second nine was a completely different story for Immelman. He knocked his approach to 5 feet to set up birdie at the first. The South African recorded back-to-back birdies from the third, both inside 10 feet, then did it again from the sixth.
At the par-4 ninth, Immelman hit a 6-iron to 4 feet and cashed in the birdie try. All tallied, it was six birdies in his final nine holes that gave Immelman a piece of the lead.
'I just caught some momentum there on that nine holes and it was nice to convert all my chances,' said Immelman, who is winless on the PGA TOUR. 'There's a premium on hitting the ball in the fairway and from there, you can take advantage of a couple of holes.'
Haas, who was born in the Charlotte area, teed off on the 10th and his front nine was horrible. He made bogey from the fairway at the 12th, and drove under a tree at the 15th. Haas made those two bogeys and made the turn at plus-2.
Like Immelman, the second nine was what put him atop the leaderboard. He tapped in a short birdie putt at the second, eagled the par-5 fifth, and recorded three birdies in a row to close his round.
Haas has struggled so far this season on the PGA TOUR. He has made only six cuts in 11 starts with his best finish a tie for 15th last week in New Orleans.
'It's only a 68. It's only 4 under,' acknowledged Haas, whose father Jay and brother Jay Jr. are also in the field this week. 'If it was 64 coming off the year I've had, that might surprise me a little bit.'
Defending champion Vijay Singh, Phil Mickelson -- who owns the last two major titles -- and Ernie Els, playing here this week for the first time, highlight a group at 1-under-par 71.