Gil Morgan and Mark McNulty each carded rounds of 4-under-par 68. They were joined in second place by Tom Wargo and Jerry Pate. Bob Murphy and Craig Stadler are one stroke further back at minus-3 at The Westin Savannah Harbor Resort and Spa.
Haas opened his round with a birdie on the first. He gave that stroke back with a bogey at the par-3 third. The two-time winner on the Champions Tour quickly got that stroke back as he chipped in for birdie on the fourth.
'No. 4 really turned things around,' Haas said. 'I never expected to make four there.'
The 52-year-old parred each of his next three holes before sinking a birdie on No. 8. Haas got to 3 under as he birdied the par-4 10th from 10 feet out. He made it two in a row with an up-and-down birdie at the next.
Haas birdied the 14th to take the outright lead at minus-5. He came right back with a birdie at 15. He parred the final three holes to lead by two after round one.
'It was a good start, you need to do that in a three-round event,' said Haas. 'The birdies on 14 and 15 turned a good round into a very good round.'
Morgan did all his damage in the middle of the round. He collected birdies on five and seven. The 59-year-old made the turn at 3 under thanks to a birdie on No. 9. Morgan picked up his final birdie at the 11th before closing with seven consecutive pars.
McNulty was one under through eight holes with a birdie on the fourth. He turned in minus-2 after a birdie on the ninth. The Zimbabwe native poured in his third birdie at 11.
The 52-year-old faltered to a three-putt bogey on 12, but atoned for that mistake with a 7-foot birdie putt on the par-4 14th. McNulty birdied 16 to share second.
'My first six tournaments haven't been good, so I made a couple of changes with my swing,' McNulty said. 'I'm happy to shoot a 68.'
Wargo got off to a good start with birdies on one and four. He stumbled to a bogey at the par-4 sixth, though. The 1994 Senior British Open champion birdied three of the first five holes on the back nine to get to minus-4.
Pate, who won the Outback Steakhouse Pro-Am earlier this year, started his round with birdies on the second and fifth. He tripped to his first birdie on the sixth. The 1976 U.S. Open champion drained back-to-back birdie efforts from No. 7.
The 52-year-old Pate gave another stroke back to par as he bogeyed the ninth to make the turn in minus-2. Pate collected birdies on 14 and 17 to end at 4 under par.
Defending champion Des Smyth opened with a 2-under-par 70. He stands alongside Jim Albus, Morris Hatalsky, 2004 champion Hale Irwin, Peter Jacobsen, Mark Johnson, Mike Reid and Scott Simpson in eighth place.