American Gene Sauers earned a three-stroke lead after the third round at the U.S. Senior Open in Oklahoma on Saturday.
Sauers, a three-time winner on the PGA Tour, surged clear of his better-known rivals with two birdies in the final three holes for a three-under-par 68 in oppressive heat at Oak Tree National in Edmond.
He posted a seven-under 206 total, while compatriot Scott Dunlap (72) and German Bernhard Langer (71) were equal second on four-under.
Halfway leader Colin Montgomerie of Scotland struggled to a 74 to fall four strokes behind.
(Reporting by Andrew Both in Cary, North Carolina, Editing by Gene Cherry)