Patrick Reed has extended his advantage at The Barclays after he recorded a second-round score of 68.
The world number 14 has been one of the most consistent performers on the PGA Tour this summer with six successive finishes above 22nd position, and he appears on course to continue that record at the first tournament of the Fedex Cup playoffs.
The American registered three bogeys on Friday but his six birdies ensured that he moved away from the field with previous joint-leader Martin Laird only hitting a 72.
Emiliano Grillo and Rickie Fowler are two shots adrift in a share of second spot while Ryan Moore is in fourth after moving seven places up the leaderboard.
However, the biggest improvement was made by Jordan Spieth, who now sits in a tie for fifth position, alongside world number one Jason Day, after a round of 67.
Rory McIlroy and Luke Donald are both six shots off the lead in a tie for 18th.
