(Reuters) - American Bubba Watson surged to the lead as Englishman Paul Casey plunged four strokes behind after the third round of the Memorial tournament in Dublin, Ohio on Saturday.
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.
"I just kept my head down, grinding away. Shooting in the 60s every day is my goal. It's working out so far," Watson told CBS television after the round.
Watson made his move with five birdies in the first seven holes, charging to the turn in four-under.
He was much more subdued on the back nine, coming home in one-over, including a bogey at the par-four 18th, where he sprayed his second shot right of the green.
Matsuyama, meanwhile, was in contention for the second successive week after sharing the lead going into the final round at the Colonial, where he tied for 10th behind winner Scott.
Scott continued to justify his ranking as world number one with another impressive round that included a 25-foot eagle at the par-five 15th.
"It's feeling good this week, better than last week," he said ominously.
(Reporting By Andrew Both in Cary, North Carolina; Editing by Larry Fine)