Dustin Johnson is on top of leaderboard at the halfway stage of the Northern Trust.
The American is one shot ahead of Jordan Spieth after two rounds of the PGA Tour's play-off event.
Meanwhile Tiger Woods was forced to withdrew before Friday's round because of "mild oblique strain that led to pain and stiffness".
The third round gets underway later on Saturday.

Mumbai's IPL campaign fizzles amid Bumrah's barren run
Iran women soccer players thank Australian government for protection
Villa's Watkins looking to make late push for England World Cup squad
Former Arsenal, Juventus goalkeeper Manninger dies in road accident
French Open prize money increases, retiring players to be honoured
