Rory McIlroy carded a one-under 69 to be in a share of the lead at the halfway mark of the BMW Championship.
Looking for his first win of 2020, the Northern Irishman sits at one under in difficult conditions at the Olympia Fields Country Club.
McIlroy got to three under in his second round at the FedEx Cup play-offs event, but dropped two shots on his final five holes.
The 2012 champion shares a one-stroke lead with American Patrick Cantlay (68).
Overnight leader Hideki Matsuyama (73) and world number one Dustin Johnson (69) are tied for third.
A two-time winner of the tournament, Johnson made back-to-back birdies to finish his round.
Adam Scott (69), Brendon Todd (68), Louis Oosthuizen (69), Tony Finau (71) and Billy Horschel (71) are tied for fifth at one over.
A shot further back are Mackenzie Hughes (73), Kevin Kisner (70) and Bubba Watson (70).
Defending champion Justin Thomas fell further back, carding a four-over 74 to be at seven over.
While there is no 36-hole cut at the BMW Championship, Tiger Woods and Jason Day are in danger of missing the Tour Championship.
Woods struggled to a 75 to be at eight over, two shots better off than Day (74).
With the top 30 qualifying for the Tour Championship, Woods is projected to be 63rd in the FedEx Cup standings, while Day is 58th.