US Open champion Matt Fitzpatrick shot an eight-under 63 as he grabbed a one-shot lead heading into the final round of the RBC Heritage at Hilton Head.
The Sheffield star, chasing his second US win to go with his major triumph, holed his second shot for an eagle two at the fourth and added six birdies for his lowest round on the PGA Tour.
For Shane Lowry, it was 74 - his highest round of the week - as he slipped back to even par. The Offaly man started brightly with a birdie at the second, but picked up bogeys at three and eleven, before frustratingly double bogeying the last.
Fitzpatrick holds a one-shot lead over Patrick Cantlay, who lost in a play-off to Jordan Spieth a year ago, after Cantlay shot a 66.
That was matched by Spieth, seeking to defend a title for the first time, who is a shot further back on 12-under par, one ahead of a group including England's Tommy Fleetwood, overnight leader Jimmy Walker and world number two Scottie Scheffler.
Former US PGA champion Walker, who opened with two rounds of 65 for a three-stroke halfway lead as he looks to rebuild a career blighted by illness, was tied with Fitzpatrick before three bogeys on the back nine.
Fitzpatrick has struggled for much of the year, missing four cuts in seven events before tying for 10th at the Masters last week, only his second top 10 of the season.
"I think this is a golf course that's shown that there are low scores around here this week," Fitzpatrick said following his round.
"Aside from Augusta, it’s my favourite golf course."
Masters champion Jon Rahm remains six shots off the lead after a third-round 69, alongside English pair Justin Rose and Aaron Rai, who slipped down the leaderboard with rounds of 72 and 71 respectively.