American golfer Bubba Watson surged to the lead as Englishman Paul Casey plunged four strokes behind after the third round of the latest PGA tour event in Ohio.
Masters champion Watson used his astonishing power to compile five early birdies on his way to a three-under-par 69 in ideal conditions at Muirfield Village.
The left-hander posted a 12-under 204 total, one stroke ahead of compatriot Scott Langley (67) with one round left.
Young Japanese player Hideki Matsuyama (69) was two strokes behind, while world number one Adam Scott of Australia (68) trailed by three despite a bogey at the final hole.
Casey, who started the day with a three-shot lead, had a nightmare round, struggling from start to finish as he carded four-over 76 to fall four strokes off the pace.