Stacy Lewis closed strong and took advantage of a costly mistake by Ai Miyazato on Sunday to take a 3-stroke victory at the RR Donnelley LPGA Founders Cup.
Lewis fired an 8-under 64 to finish the tournament at 23-under-par 265 and capture her seventh career LPGA victory.
Miyazato entered the day with a 4-stroke lead. Lewis was charged with a 2- stroke penalty at the end of Saturday's round for her caddie testing the surface of a bunker. She managed just a 1-under 71 in her final round at Wildfire Golf Club at JW Marriott Phoenix Desert Ridge Resort & Spa to take second place at 20-under-par 268.
With the win, Lewis overtook Yani Tseng for the No. 1 ranking in the world, becoming the first American since Cristie Kerr in Oct. 2010 to hold the spot.
"It kind of has a nice ring to it," Lewis said about her new ranking.
Angela Stanford (68) sat alone in third place at 17-under, while Jessica Korda (66), Giulia Sergas (68), Lizette Salas (69) and Jee Young Lee (71) shared fourth at 16-under.
Lewis quickly started to make her push towards Miyazato as she birdied four of her first nine holes.
Miyazato, meanwhile, recorded just two birdies and seven pars over that span to hit the turn with a 2-stroke lead before she opened her inward nine with a birdie at the 10th.
Lewis got that stroke back with a birdie at the 11th, but then stumbled to her lone bogey of the day at the 12th to fall back into a 2-stroke deficit.
She quickly responded with a birdie at the 13th and got within a stroke at the 14th with a par coupled with Miyazato's bogey.
After they both birdied the 15th, Miyazato's second shot at the par-4 16th found its way into a shrub to the left of the green and she was forced to take an unplayable lie, resulting in a stroke penalty.
Miyazato then chipped her next shot well past the hole and 2-putted for a double bogey to drop to minus-20.
"I hit the pitching wedge, but my instinct said that it was an easy nine, so it was a little bit indecisive and that's why I pulled my shot," Miyazato said about the decisive hole. "It's a little unlucky I thought."
Lewis, however, hit her approach about 20 feet from the pin and rolled in her birdie putt at the same hole to move to 22-under and take a 2-stroke lead.
She gained a little more cushion with her third straight birdie at the 17th, and then hit her second shot at the 18th within 10 feet and 2-putted for par to close out the victory.
Miyazato, who held the No. 1 ranking prior to Kerr, failed to make a late push by closing with consecutive pars.
"With everything that happened yesterday, I kind of had my back against the wall again. I was pretty comfortable in that position," said Lewis. "I just wanted to play well for Travis (her caddie) today. He deserved it and this one's definitely for him."
NOTES: Kerr was the only other American to reach No. 1 ... Lewis will become the seventh player to hold the top spot in the Rolex Rankings ... Lewis' previous best finish at this event was a tie for 10th in 2012 ... It was Lewis' second straight win. She was coming off a victory at the HSBC Women's Champions two weeks ago ... Yani Tseng, who held the No. 1 ranking for 109 consecutive weeks before Lewis, carded a 2-under 70 on Sunday to finish in a tie for 59th place at 4-under-par 284.