SAN DIEGO -- Top-ranked Jon Rahm and Justin Thomas made the birdies they needed to keep pace on the easier North Course at Torrey Pines on Thursday and shared the lead with hard-charging Adam Schenk after two rounds of the Farmers Insurance Open.
Schenk made eight straight birdies to shoot a career-low, 10-under 62, also on the North Course, and joined Rahm (65) and Thomas (63) at 13-under 131.
The 30-year-old Schenk, who grew up on an Indiana sod farm, started his impressive run of birdies on the fourth hole and ended it on No. 11. He also birdied Nos. 16 and 17 in his bogey-free round.
All three leaders opened Wednesday on the South Course, where Rahm won the U.S. Open last year for his first major. Rahm also got his first PGA Tour victory in 2017 at Torrey Pines, a municipal facility on the bluffs overlooking the Pacific Ocean.
The final two rounds will be played on the South Course.
Schenk recorded the longest consecutive birdies streak at this tournament since 2003.
"I lost track of how many I made in a row, but there was a lot of low scores on the North Course yesterday and I knew there was a lot of gettable holes and I needed to keep going if I wanted to get up on top of the leaderboard and hopefully stay there throughout the weekend," Schenk said. "So I know I had to try to keep the pedal down and not get satisfied with how many birdies I made."
Schenk struggled to hit fairways, but his approaches were good enough to give himself reasonable birdie chances.
"Just a lot of long putts," he said. "It's not like I was hitting it to 10 feet every time making the putts. I had a lot of lengthy ones."
Schenk said he made eight birdies in a row in an age-group championship in his early teens.
"So I had done it before, obviously not on the PGA Tour, on this stage. I just lost track and knew I had some par 5s coming up and wanted to take advantage of them. Luckily I hit some good shots on 9 and then 10 I made a long putt," he said.
The Farmers Insurance Open is being played Wednesday through Saturday to avoid a television conflict with the NFL's two conference championship games on Sunday.
Rahm closed his opening round Wednesday with an eagle for the best score of the day on the South Course. The Spaniard birdied five of his first eight holes on the North on Thursday before making his only bogey.
"I mean, it wasn't bad yesterday, it certainly wasn't bad today," Rahm said. "I managed really well today and it feels good because if you tell me before the round I'm going to hit four fairways and shoot 7-under, I'd tell you that something out there must have been really good, which today was. For how little fairways I hit, I was able to hit a lot of those greens from the rough, which is not the easiest thing to do."
Thomas, playing the Farmers Insurance Open for the first time since 2015, had nine birdies in his bogey-free round.
"I played well, I drove it well, something you've got to do out here on the North Course," Thomas said. "I mean, both courses, but if you drive it well, you've got a lot of wedges, a lot of short holes, four par-5s. Made some nice putts when I needed to, just kind of some of those short mid-rangers and it was a solid day."
Billy Horschel, who opened with a 63 on the North, struggled through a 1-over 73 on the South and dropped five shots off the lead. He made a double-bogey 6 on No. 14.
The featured afternoon threesome of Jordan Spieth (78), Rickie Fowler (76) and Bryson DeChambeau (72) all missed the cut, with the big-hitting DeChambeau grabbing at his lower back in apparent pain on several occasions.