Steve Stricker dominated the second day of the US PGA Tour's season-opening Tournament of Champions with a 10-under-par round of 63.
The 44-year-old American carded eight birdies and an eagle to take a five-shot lead at the halfway stage on 15 under in Hawaii.
"This game is never easy, but I had it going today," said Stricker.
A double bogey at 17 saw Scot Martin Laird shoot a three-under par 70 and slip to joint fourth on eight under.
Stricker was already six under for the day when he eagled the par-five 15th, after hitting a three wood to within 12 feet of the hole.
At number six in the world the highest-ranked player in the 27-man field, he added birdies at 17 and 18 to finish with a flourish.
"I felt like I was going to make every putt I looked at there for a while and I gave myself a lot of opportunities, which is the key," he said.
Despite a five-shot cushion, he refused to get carried away with two rounds remaining at the Plantation Course in Kapalua.
"We're halfway through," he said. "We've got a long ways to go yet."
Webb Simpson posted his second straight round of 68 to move second on 10 under, while South Korea-born American Kevin Na climbed into third place with a record-equalling back nine.
Na was level par for the tournament after eight before a sudden burst burst saw him shoot nine under over the last 10 holes, including back-to-back eagles.
The 28-year-old holed out with a five-iron from 221 yards at 17 before sinking a 10-footer at 18 for a back-nine 29 that matched the course record set by Vijay Singh in 2004.
"That was a lot of fun. All of a sudden on the back nine I started getting it together," said Na, who trails Stricker by six shots.
"At 18 I hit a beautiful second shot into the green and I just kept telling myself 'for 29, for 29'. As soon as I hit it, I knew it was in."
went round in 71 and shares fourth place with Laird, who recovered from a double bogey at the 17th to finish with a birdie.
An eagle and five birdies helped Rory Sabbatini salvage a round of 70 after he was penalised two strokes for arriving late to the first tee.
Chris Kirk almost carded an albatross when his second shot at the five-par fifth caught the lip of the cup. He sits joint seventh on five under.