Pat Bates, who played in the final group Saturday with Hnatiuk, is alone in fifth at 13-under-par, followed by Tripp Isenhour (64), Neal Lancaster (64) and reigning PGA Champion David Toms (65). The trio is tied for sixth at minus 12.
Hnatiuk owned a one-shot lead after the second round but extended the lead as he went 2-under through his first six holes. At the par-4 seventh, Hnatiuk chipped in from the side of the green and two holes later he sank a 30-footer to make the turn at 16-under-par.
Hnatiuk missed a four-foot par save on the 10th to cut his lead to one over Bates. But Hnatiuk quickly increased his advantage, knocking an 8-iron to eight feet at 11 to set up birdie. He chipped in for birdie at the next hole after his approach spun off the putting surface.
With a three-shot lead, Hnatiuk parred the next three holes as Begay was charging to the top of the leaderboard. Begay, known for putting left-handed or right-handed depending on the break of the putt, ran home a five-foot birdie at the 16th to reach 15-under-par and cut Hnatiuk's lead to two.
Hnatiuk's second at the par-5 16th ran through the green into a chipping area behind the hole. His third shot landed inches from the hole and he tapped in the birdie to reclaim a three-shot edge.
Begay popped up his drive on 18, barely making it to the fairway. He had 193 yards into the hole and his 4-iron approach missed right of the green and wound up in a bunker. Begay failed to get up and down, bogeying the hole and giving Hnatiuk a four-shot cushion.
Hnatiuk missed a birdie putt on 17 and scrambled to make par at 18 after missing the green. Now the Canadian takes the lead into the final round of a PGA Tour event for the first time in his career.
'Obviously, I'm happy with the position I'm in. I don't know how to react because I've never been in this position with any kind of lead. I'm looking forward to it,' said Hnatiuk.
Begay has four victories on the PGA Tour and in three of those he had to chase down the leader. Begay thinks that Hnatiuk will have to battle his nerves Sunday if the Canadian is to make his first trip to the winner's circle.
'It's just a fact of life,' said Begay, who is returning to form after injuring his back before last season. 'Everybody who's won, who's been there, knows that. Now it just depends on how Glen handles it. He handled it great today. It didn't look like it affected him in the least.'
'Anybody in that pack has a chance to win I suppose. If I let it,' said Hnatiuk. 'I'm not going to do anything stupid, not going to take any crazy chances. But I still have to go on, go forward.'
Begay, the 2000 champion at the TPC at Southwind, shot a third-round 68.
Petrovic had an erratic round Saturday with nine birdies, four bogeys and five pars. He shot a 5-under 66 and will play with Hnatiuk in Sunday's final round.
Kuchar closed his round with four birdies in a row to shoot a 67 and get into the group at 14-under-par 199.
Full-field scores from the FedEx St. Jude Classic