Dustin Johnson fired a 4-under 67 to take the lead into the weekend at The Northern Trust on Friday, and sits at 12-under through 36 holes.
Jordan Spieth shot a 7-under 64 to move into second at 11-under for the tourney, while Jon Rahm is among four golfers tied at 10-under.
Among those sitting two strokes back is Troy Merritt, who tied the Liberty National course record Thursday with a 62.
Rory McIlroy moved within three shots of the lead with a 3-under 68, but his round had some drama. The world's No. 3-ranked golfer was initially handed a two-stoke penalty for a mix-up in the bunker on the 14th hole before the penalty was rescinded.
Tiger Woods withdrew from the tournament Friday morning, citing an oblique strain.