HILTON HEAD ISLAND, South Carolina (AP) ― Carl Pettersson couldn’t have had a better time with Colt Knost at the RBC Heritage. He hopes to have as much fun when the two play again on Sunday.

Pettersson had a run of five straight birdies on the front nine and finished with a birdie on the 18th hole for a 66 and a one-stroke lead over Knost heading into the final round of the RBC Heritage on Saturday.

Pettersson and Knost chatted and laughed throughout the round, looking more like a pair of duffers at the local muni out for a weekend round rather than pro golfers chasing a PGA Tour title. “Two fat guys played in three hours, 48 minutes,” Pettersson said with a smile. “That was pretty good. But we had a good time.”

Especially Pettersson who used his birdie streak to overtake a nervous Knost and build a three-shot lead through 10 holes. Knost tamed the butterflies enough to find the game that had him in the lead here after Thursday and Friday, tying for the top after Pettersson’s bogey on the par-5 15th hole.

Pettersson moved in front at the end with a stunning approach that slid by the cup on No. 18 for a closing birdie. The two will match up once again in the final pairing Sunday.

“I’m going to try tomorrow to have fun,” said Knost, seeking his first win on the PGA Tour.

Zach Johnson, the 2007 Masters winner, shot a 66 to move to third at 8 under, three behind the leaders. Two-time RBC Heritage champion Boo Weekley had a 70 and was in fourth another shot behind. Defending champ Brandt Snedeker (69), Kevin Na (70) and Robert Garrigus (70) were next at 6 under.

World No. 1 Luke Donald failed to make a move toward keeping the top spot, his even-par 71 leaving him at 2 over and tied for 52nd. Donald needs to finish eighth or better to fend off No. 2 Rory McIlroy.