The 18-year-old Ko never had the lead Sunday until she rolled in a 5-foot birdie putt on the par-5 18th hole for her seventh career victory. She also made birdie on the 18th in regulation for a 2-under 70 to force a playoff.
Pressel closed with a 72. She missed three birdie putts on the 18th hole — from 15 feet in regulation, from 10 feet on the first playoff hole and from 8 feet on the second playoff hole.
Canadian Brooke Henderson, the 17 year old from Smiths Falls, Ont., had a 74 and missed the playoff by one shot.