The Australian's six-under 66 left him hot on the heels of co-leaders David Toms and Canada's Stephen Ames, who both shot bogey-free rounds on Friday.

Of the top-six golfers, Pampling fired the most birdies – eight – along with Ken Tanigawa, who is also one behind the lead with South Korean Y.E. Yang and Lee Janzen.

It is a crowded leaderboard but Pampling could have had the outright lead had it not been for back-to-back bogeys on 4 and 5.

But he finished in a flurry with five birdies, including on 17 and 18, to fire warning shots at Toms and Ames.

Also in the mix are Paul Goydos, Spaniard Miguel Angel Jimenez and German Bernhard Langer at five-under 67.

Langer, age 65, would break the all-time Champions Tour record with one more victory as he is tied with Hale Irwin at 45 for his career.

Toms picked up a pair of victories in March at the Cologuard Classic and the Galleri Classic. After tying for third last week at the Insperity Invitational, he's in second place in the Charles Schwab Cup money standings.

Toms started his round on the back nine at TPC Sugarloaf and made three birdies going out before piling on four more on the second nine. It was posed to Toms in the media centre that he was on a heater.

"That's what I tried to do when I was on the (PGA) Tour. When you felt good about your game, you needed to capitalise on it," Toms said.

"When you were confident, you needed to play well. There's so many days that can beat you up and you can't score that when you are playing well, you need to take advantage of it.

"That's where I feel like I am right now. I feel good about my tee ball, I feel good about iron shots, judging distance properly, speed's been pretty good on the greens lately and I've made my fair share."

Ames, who won the Trophy Hassan II in February, also opened on the back nine. He made the turn with a pair of birdies – the par-5 18th and the par-4 1st – and added three straight at Nos.6-8 before finishing up.

Ames won the Mitsubishi Electric in 2017, though he said TPC Sugarloaf is a different course these days.

"I think overall the condition of the golf course is awesome," Ames said. "A little thin in some areas, but overall the condition of the golf course is very nice, and the weather's been holding off, which is even better. So we'll see what happens for the rest of the weekend."