(Reuters) - Former U.S. Open champion Lucas Glover, boosted by a 50-foot birdie, carded six-under-par 65 to surge into the third-round lead at the Shriners Hospitals For Children Open in Las Vegas on Saturday.

Glover took a while to adjust to the slow pace of the greens at TPC Summerlin, but there was no stopping him once he rolled in a monster putt at the eighth hole.

He followed up with an eagle at the next en route to a 15-under 198 total, one stroke better than Brooks Koepka (70) and halfway leader Rod Pampling (71), with Geoff Oglivy and Russell Henley two behind.

"I didn’t have the speed of the greens down the first few holes and I struggled with it the first seven holes," Glover said.

The South Carolinian was a surprise winner of the rain-plagued 2009 U.S. Open at Bethpage in New York, but instead of kicking on from that major success he has won only once since.

Glover, who has gone through a divorce and struggled with a knee injury, has not finished in the top 100 on the PGA Tour points ranking for the past five seasons but showed glimpses of form with a tie for fifth at last week's event in Mississippi.

Pampling, who shot a sizzling 11-under 60 in the first round, could not replicate that form and by day's end was happy simply to be within a shot.

"Nothing special," the Australian said of his performance.

"Thankfully, with that good score on the first day, I’ve been able to have a so-so day, so tomorrow I have to go low."

Koepka was also downbeat about his form and, like Glover, had trouble adjusting to the greens.

"Ball striking was pretty poor and for some reason I couldn’t get the speed of the greens," he said.

(Reporting by Andrew Both in Cary, North Carolina; Editing by Peter Rutherford)