Jordan Spieth caught fire on the greens Friday as he seized a share of the halfway lead at the Northern Trust, the first tournament in the US PGA Tour's FedEx Cup playoffs.
Spieth's seven birdies included five in a row from the 10th through the 14th -- six in all on the back nine in a five-under par 65 that gave him a six-under total of 134.
He completed a group of four sharing the lead that also included world number one Dustin Johnson, Venezuela's Jhonattan Vegas and Rickie Fowler.
Vegas also posted a 65, nabbing five birdies without a bogey. Fowler carded a 66 and Johnson posted a one-under 69 on the Glen Oaks Club course in Old Westbury, New York.
Johnson, whose opening round 65 put him one off the overnight lead, was three-under through 12 holes and eight-under for the tournament before errant tee shots led to back-to back late bogeys.
"Other than that, I felt like it was a really solid day," Johnson said. "I'm really pleased with the way the golf game is right now and I'm looking forward to this weekend."
Reigning British Open champion Spieth had dropped out of the leading group with a bogey at the 15th, but he rebounded with a 40-foot birdie putt at 16.
"I put in a little work in an early session before my warm-up session today," said Spieth, who also drained a 23-footer at the 12th. "I just was messing around a little with alignment and ball position."
"I've been trying to figure out my alignment for a while and I just kind of threw it out the window and said we're just going to go speed -- if you pull it, you push it, so be it -- just try to and feel putts out here."
Matt Kuchar and Bubba Watson were a stroke back from the leaders on 135.
Kuchar rebounded from a rough start with a string of eight birdies in 10 holes to finish at 64 for the day. Watson signed for a 68.
Spain's John Rahm, England's Justin Rose and overnight leader Russell Henley were a further stroke back on 136, and eight players were tied on 137, including PGA Championship winner Justin Thomas, defending Northern Trust champion Patrick Reed, England's Paul Casey and Colombian Camilo Villegas.
Reigning FedEx Cup champion Rory McIlroy, whose 2017 campaign has been hindered by injury, was seven shots off the lead after a 68.
Japan's Hideki Matsuyama, who came into the tournament atop the FedEx Cup standings, was destined for an early exit after a one-under 69 left him three-over for the tournament and outside the projected cut line.