Brooks Koepka knows he has lot to learn about the PGA Tour, and the former All-American at Florida State is proving to be a very quick study.

Koepka shot a 3-under 67 Friday to turn a lead he shared with two others after 18 holes into a solo lead by a stroke after the second round Friday at the St. Jude Classic. It's just his second time with at least a piece of the 36-hole lead on the PGA Tour, and puts him halfway to what could be his second career title and second since the start of February.

"I'm still 25," Koepka said. "I've been out here for a year now. Just trying to learn and make sure I'm ready for the majors, make sure I'm ready for five years from now. I just got to be patient."

Koepka, who won in Phoenix in February, shared the first-round lead with Ryan Palmer and Greg Owen. He turned in a four birdie-one bogey round for a 9-under 131.

"Playing solid golf, no mistakes, being very patient, waiting for my opportunities to come," Koepka said. "And when they have come, I've kind of taken advantage of them, but I still feel like I could be about 5, 6 under par ... Really haven't been firing on all cylinders, but good enough to be at the top."

Austin Cook (64) was at 132. The Arkansas native is playing his tour event after getting a sponsor's exemption after he tied for 11th in Houston earlier this year as a qualifier. He had plenty of support, too, as he lives less than 90 minutes away.

"I'm sure lot more buying tickets right now to come tomorrow," Cook said after matching the best round of the day.

TPC Southwind played firmer with temperatures in the 90s drying out the course, and that has greens playing faster along with some tricky pin placements Friday.

Koepka only added this event at the deadline to help tune up his game for the U.S. Open at Chambers Bay in Washington. He hit 14 of 18 greens for a second straight round and needed 28 putts Friday. He likes his chances going into the weekend as he tries to join Rory McIlroy, Jordan Spieth and Jimmy Walker as multiple winners on tour this season.

"I haven't blitzed the golf course yet," Koepka said. "You can shoot 8, 9 under in a round out here. I feel like the greens are so good, you put the ball in the fairway you really take it 8, 9 under. Being in the lead is nice, but would have liked to have been a few more under par."

Steve Alker briefly had the lead at 10 under with two holes to play only to finish bogey-double bogey. He had a 68 for a 133 total and needed only 23 putts Friday as he got to 10 under with his sixth birdie of the round. The New Zealand native who now lives in Arizona said he wasn't aware he was the first to 10 under.

"It's a good thing it's not Sunday and finish two behind that would be bad," Alker said. "You have to look at the positives and say, 'I've got two days left.' I've been swinging it pretty good and still learning the putter, so there's a lot of good things going on."

Chris Smith (67), Russell Knox (64) and Greg Owen (70) were among seven tied at 134. Palmer (71) was tied with three others at 135.

At one point Friday, as many as five were tied atop the leaderboard with eight having a piece of the lead at some point.

Koepka was tied with four others when he teed off in the afternoon and promptly birdied his opening hole to take the lead to himself. Koepka, who played at Florida State and joined the PGA Tour last year, took the lead back with consecutive birdies on Nos. 15 and 16 combined with Alker's finish.

Divots: Steven Bowditch and Retief Goosen were among those missing the cut at 1 over with 76 playing the weekend. ... David Hearn had a hole-in-one on No. 4 with a 6-iron from 185 yards, and Hudson Swafford had an ace on No. 14 with a 9-iron from 169 yards. Hearn said this was his eighth overall and first since holing out on No. 8 here in a practice round with the same club.