Afternoon storms hit the TPC at Southwind and delayed play for almost four hours. The players returned to the course at 7 PM ET, but the horn sounded ending play for good at 8:39 PM.
Seventy-eight players were unable to complete their rounds and will return at 8:15 AM Friday morning.
Justin Leonard, Matt Kuchar, Garrett Willis, David Howser and 2000 FedEx St. Jude Classic winner Notah Begay III shared third place at 5-under par, while Jay Haas was 5-under through 16 holes.
Hnatiuk teed off on the back nine at the TPC at Southwind and collected three birdies and one bogey on his opening nine holes. He moved toward the top of the leaderboard on his second nine, starting at the second hole when he ran home a 12-foot birdie putt.
Hnatiuk knocked a 6-iron to six feet at the par-3 fourth to set up birdie and made it two in a row with a five-footer at the par-5 fifth.
He closed out his scoring with a six-foot birdie at No. 7.
'I hit a lot of fairways. And I hit a considerable amount of greens but the quality of iron shots I hit were very well,' said Hnatiuk, whose best finish this season was a tie for eighth at Harbour Town in April. 'I gave myself a lot of real good opportunities.'
Petrovic, who played on the Buy.Com Tour last season, was 4-under-par through 15 holes and closed with a flurry. His second shot landed in a greenside bunker at the par-5 16th and he blasted within inches of the hole.
After the kick-in birdie at 16, Petrovic roped a 7-iron to three feet at 18 to set up a birdie and complete his bogey-free round.
'I was just getting up and hitting shots and not having to fool around with it. And whatever shot I wanted to hit, low, high, draw, I could do it. It was just there,' said Petrovic. 'And I felt really comfortable on the greens.'
Leonard could have shared the lead but ran into trouble late in his round. At the 17th, he left a bunker shot on the fringe and two-putted for bogey.
'Maybe the worst bunker shot I've hit on tour,' said Leonard, who won at Harbour Town in April.
Kuchar, the Honda Classic champion, also stood at 6-under until a late mistake. He missed the fairway at 18 and had to hack his second out to the fairway. Kuchar's approach landed 10 feet from the hole but the putt lipped out and dropped him into a tie for third.
Deane Pappas, Doug Barron and Steve Pate were in the clubhouse at 4-under-par, while Jim Carter and John Daly were 4-under through 14 holes. Ted Tryba completed 11 holes with the same score.
Defending champion Bob Estes was 1-under-par through 14 holes when play was suspended.
Full-field scores from the FedEx St. Jude Classic