New York - World number two Dustin Johnson rolled in an eight-foot birdie putt at the final hole Friday to take a one-shot lead over Jordan Spieth halfway through the US PGA Tour Northern Trust.
Johnson shook off an opening bogey to card five birdies in a four-under par 67 at Liberty National in New Jersey.
His 12-under par total of 130 put him a stroke in front of Spieth -- who set the early pace with a seven-under par 64 for 131.
The second round of the tour's first FedEx Cup playoff event opened with 15-time major champion Tiger Woods withdrawing with a "mild oblique strain".
Woods, trying to end the season on a high note after ending an 11-year major title drought with his victory at the Masters in April, had struggled to a first-round 75 that left him equal 116th in the field of 120.
Woods said he remained "hopeful" that he would be able to play next week's BMW Championship at Medinah and continue his bid to make the 30-strong field to defend his Tour Championship title in the playoff finale at East Lake.
Johnson, who started the day one shot off Troy Merritt's lead, is chasing a third title in the event after winning in 2011 and 2017 -- both times at different venues.
"I feel like I'm swinging it really well," Johnson said. "I've got a lot of control with the golf ball and hitting a lot of really nice shots and rolled in a couple putts today which is nice -- but still feel like I left quite a few out there.
"I'm in a good position heading into the weekend, and if I can keep swinging the way I am, I think it's going to be a good weekend."
Spieth will be hoping to keep things going through the weekend -- something he's had trouble doing this season.
Last week at the Wyndham Championship he shot two rounds in the 60s before a third-round 77 saw him miss the 54-hole cut.
"The important thing for me is not to get ahead of myself," Spieth said. "It's to just continue trying to be consistent. Historically, I'm a very consistent player. I've lost a bit of that.
"I still have that firepower, but the consistency is what I'm trying to get back."
Merritt, who matched the course record with a nine-under 62 on Thursday, fell back with a one-under 70 to join a group sharing third on 132. He was joined by former Masters champion Patrick Reed, who posted his second straight 66, Spain's Jon Rahm, who carded a 68 and Mexico's Abraham Ancer, who fired a 65.
Northern Ireland star Rory McIlroy was among five players on 133 -- but not before officials rescinded a two-stroke penalty he was assessed during the round.
McIlroy was two-under for the day through 13 holes when he found a greenside bunker at 14.
Noticing what he thought was a stone nestled against his ball in the bunker McIlroy, in accordance with the new rules instituted this year, went to move the loose impediment only to find it was a clump of sand.
A rules official on the course determined he had therefore violated the rules, even though McIlroy didn't believe he had improved his lie and hadn't touched the sand on purpose.
After his round however, the penalty was rescinded and McIlroy signed for a 68 that left him just three shots off the lead.
Leading scores after Friday's second round of the US PGA Northern Trust tournament in Jersey City, New Jersey (par-71, USA unless noted):
130 - Dustin Johnson 63-67
131 - Jordan Spieth 67-64
132 - Abraham Ancer (MEX) 67-65, Troy Merritt 62-70, Patrick Reed 66-66, Jon Rahm (ESP) 64-68
133 - Andrew Putnam 69-64, Justin Rose (ENG) 65-68, Louis Oosthuizen (RSA) 68-65, Wyndham Clark 67-66, Rory McIlroy (NIR) 65-68
134 - Ian Poulter (ENG) 68-66, Kevin Kisner 64-70, Harold Varner 67-67
135 - Brian Stuard 66-69, C.T. Pan (TPE) 68-67, Justin Thomas 67-68, Im Sung-jae (KOR) 67-68, Andrew Landry 68-67
136 - Joel Dahmen 67-69, Dylan Frittelli (RSA) 69-67, Bryson DeChambeau 68-68, Hideki Matsuyama (JPN) 68-68, Shane Lowry (IRL) 69-67, Kevin Na 69-67, Danny Willett (ENG) 66-70
137 - Corey Conners (CAN) 66-71, Ryan Palmer 70-67, Patrick Cantlay 70-67, Vaughn Taylor 69-68, Max Homa 66-71, J.T. Poston 67-70, Adam Scott (AUS) 68-69