Paul Casey and Charl Schwartzel lie four shots back after Bubba Watson established a one stroke lead after the third round of the Memorial Tournament in Ohio.
Watson carded a second successive 69 to add to his opening 66 as he and fellow left-hander Scott Langley secured their places in the final group on Sunday.
Five birdies in six holes on the front nine took Watson to the fore, the highlights being excellent approaches to six feet at the third and eight feet at the sixth.
He was six inches short of an eagle at the par five seventh, with his good run of holes marred only by a bogey at the fourth.
Dropped shots on the 11th and 18th restricted his lead, though he added one more birdie with a 12-foot putt on the 15th to ensure a third sub-70 round.
Japan's Hideki Matsuyama is a shot further back at 10 under after a closing 15 foot birdie putt gave him a round of 69.
World Number One Adam Scott is alone in fourth at nine under, Casey recorded a disappointing 76 to slip down the leaderboard to eight under, though he is in good company in a group containing young sensation Jordan Spieth, who shot 67, and Major winner Schwartzel.
Rory McIlroy is among the group on six under after following up his 78 on Friday with a three under par 69 on Saturday.
