A closing five-under 67 packed with seven birdies around the turn, for a 21-under 267 total, left the 34-year-old Englishman a stroke better than Denmark’s Thorbjorn Olesen and fellow Briton Gary Boyd.
“My putting had been letting me down so when I read the book I decided to use some of the tips in it,” said former teaching-pro Rock, who flirted with a maiden victory last year before losing a playoff to amateur Shane Lowry in the Irish Open.
“And it’s helped me considerably.”
By the time Rock began his round he had been overtaken by the charging Olesen who went out in just 29, 6-under-par.
The Dane set the target of 20-under by ramming home a 30ft birdie putt on the last for a round of 62 and Rock slipped four shots behind him with a bogey on the third in a nervy start.
But Rock then got to grips with his task and a sixth birdie in seven holes from the fifth finally put him back on top of the leaderboard on his own at the 11th.
He then dropped his second shot of the day but quickly repaired that damage with a birdie at 13.
Rock’s 15-footer to save par on the 17th after driving deep in trees proved to be just as important as any of his birdies.
“That putt on the 17th took a huge amount of pressure off,” he said.
Boyd’s 66 also took him to 20-under but a solid par on the 18th ensured Rock broke his tour duck.
Italian teenager Matteo Manassero found himself too much to do to achieve his dream of winning his home open 13 months after turning professional at the tournament. Manassero’s 68 left him five shots adrift of Rock.
Like the winner, 18-year-old Manassero makes his US Open debut next week.
Karlsson clings to lead in St. Jude Classic
In Memphis, Tennessee, Robert Karlsson shot a 2-under 68 on Saturday to remain atop the leaderboard through three rounds in the St. Jude Classic.
Karlsson looked ready to run away from the field, leading by five strokes on the back nine, but the Swede closed with his only bogey of the day, dropping to 11 under and one stroke ahead of Harrison Frazar.
Frazar shot a 64. John Merrick (67) was third at 8 under.
The 41-year-old Karlsson, an 11-time winner on the European Tour, is trying to become the seventh first-time winner on the PGA Tour this year and the first in Memphis since Dicky Pride in 1994.
LPGA State Farm Classic
In Springfield, Illinois, top-ranked Yani Tseng shot her second straight 6-under 66 to take a one-stroke lead over Mindy Kim in the LPGA State Farm Classic.
Tseng reached 17 under, birdieing all four of Panther Creek’s par 5s in her bogey-free round. She won the season-opening LPGA Thailand for her sixth tour title in four years.
Kim, the leader after the first two round, bogeyed the final hole for a 69. Brittany Lincicome, coming off a victory Sunday in New Jersey, shot a 66 to join Shanshan Feng (69) at 14 under. Defending champion Cristie Kerr (66) was another stroke back at 13 under.
