Karlsson birdies keep him on course for honours at Memphis

Aiming to go one better than his runner-up placing last year, Karlsson was involved in an intriguing battle with his American playing partner Frazar, who twice drew level through the front nine.

The 41-year-old Swede forged back ahead on the ninth, however, when his approach landed within inches to claim his fourth birdie and bounce back immediately from his first blemish of the round.

Frazar had put the pressure on early on when he birdied the first, after chipping onto the green from the left rough, and then rolling in a 16-footer at the third to draw level.

But Karlsson, who had also opened with birdie at the first, responded with a birdie at the par-three fourth to move back ahead.

Their entertaining tussle gathered pace when both then birdied the sixth before a bogey for Karlsson at the par-four eighth drew them back together on 13-under.

But after Frazar pulled his tee-shot at the ninth right into the trees, Karlsson produced a peach of an approach to edge back ahead.

All eyes remained on the last two as the chasing pack remained at arm's length, some six strokes off the pace.

American duo Charles Howell III and Cameron Tringale were joined by Retief Goosen as the best-placed challengers at eight-under.

Defending champion and world number two Lee Westwood was just a stroke further back after he had fired an equal final-round best five-under through 16 holes.

Karlsson, who has 11 international victories, was unfazed by the conclusion to his round.

"You're going to make a mistake here and there," he said. "I'm very, very happy with the way I'm playing."

The Swede said he was not scoreboard watching as his lead slipped from five strokes to one.

"If I shoot 80 tomorrow, I might be 50th. If I shoot 60, I'll probably win. It's not even interesting where you are now," he added.

"I'm in the last group and have a great chance of getting out there tomorrow and play golf. I'm looking forward to that."

Frazar, 39, is looking for his first PGA Tour win. He said Karlsson looked so far out in front that the other players relaxed a bit and started playing better.

"About halfway through the round today, we kind of looked up and Robert was taking off again," said Frazar. "Most of us out there probably … kind of forgot about trying to win the golf tournament."

Frazar finished by rolling in a 42-foot putt to birdie the last.

"Went right in the centre," he said. "Jumped in there like a rabbit."

Meanwhile, Goosen said it would probably take more good golf to overtake Karlsson.

"On the back nine, I don't know what happened to me. Made four birdies in a row," he added.

"Need to get another round like this in tomorrow."