PHOENIX -- Mirim Lee is just getting started on the LPGA Tour -- and isn't taking baby steps.
Neither is 16-year-old Lydia Ko.
Lee shot a 5-under 67 on Friday in the JTBC Founders Cup to take a two-stroke lead over Ko into the weekend. The 23-year-old South Korean played the final eight holes in 5 under, making an eagle and three birdies to reach 13-under 131 at Desert Ridge's Wildfire Golf Club.
"I played a little boring on the front nine, so I went more aggressive on the back nine and it worked well," Lee said. "So, now I plan on being aggressive the rest of the week."
Ko, the Canadian Women's Open winner as an amateur the last two years, shot 66. The first-year pro played a late six-hole stretch in 6 under with an eagle and four birdies.
"I just gave myself more opportunities on the back nine," Ko said.
Lee is making her third start in her rookie season on the LPGA Tour after winning three times on the Korean LPGA. In her first two events, she tied for 33rd in the Bahamas and tied for 25th in the Women's Australian Open.
"I feel more comfortable because here the fairways are bigger," Lee said. "My driver shots play better here."
She holed a 35-foot birdie putt on the par-4 13th, saved par on the par-3 14th with a 20-footer, and hit a hybrid from 220 yards to 12 feet to set up the eagle on the par-5 15th.
"All this week, hybrids have not worked for me, so I felt very fortunate," Lee said.
She also birdied the par-4 18th, hitting a 9-iron to 2 feet.
Born in South Korea and raised in New Zealand, Ko won the Swinging Skirts World Ladies Masters in December in Thailand in her second start after turning pro in October. She has five victories in professional events, also winning in Australia and New Zealand.
Ko began her back-nine run with birdies on Nos. 12 and 13, eagled the 15th and birdied Nos. 16 and 17.
After going hungry on the course in the first round, she stocked up Friday.
"I had a protein bar and like a protein jelly and there's always a peanut butter sandwich in there," Ko said. "I actually noticed that it was in my bag yesterday, but I didn't find it, so it was actually more done."
Sun Young Yoo was third at 10 under after a bogey-free 65, matching the best round of the day. The 2012 Kraft Nabisco winner played the back nine in 5-under 31.
"I was more patient today," Yoo said. "Overall, everything was working very well."
"I left a lot of putts out there," Park said.
Korda and Choi shot 66, and Ryu had a 67.
Michelle Wie topped the group at 8 under, following her opening 66 with a 70. She had four straight birdies in the middle of the round to take the lead at 10 under, then bogeyed the par-5 fifth -- her 14th hole of the day -- after hitting over the green from a greenside bunker.
"I thought I hit a really good bunker shot and I flew it 15 yards past the green," Wie said. "So, that was a good one. ... It went over everyone's head."
She also dropped a stroke on the par-4 ninth.
"All day today I just felt like I could have shot a lot more under par," Wie said.
Defending champion Stacy Lewis, 2011 winner Karrie Webb, and Morgan Pressel were 7 under. Lewis and Webb shot 71, and Pressel followed her opening 65 with a 72. After playing the first 11 holes Thursday in 9 under, Pressel was 2 over on the next 25.