Hideki Matsuyama broke a course record as he claimed a one-stroke lead after the second round at the BMW Championship.
Matsuyama sizzled at Medinah Country Club, where the Japanese carded a nine-under-par 63 to top the leaderboard on Friday.
In the second tournament of the FedEx Cup play-offs, Matsuyama was flawless with his putter – nine birdies highlighting a bogey-free round in Illinois.
Matsuyama birdied five of his opening nine holes and closed the day by gaining back-to-back shots as he improved to 12 under at the halfway stage, ahead of American pair Patrick Cantlay (67) and Tony Finau (66).
Ranked 33rd prior to the event, Matsuyama is projected to move up to second with victory and he said: "I wish I knew why I putted so well today.
"But I was happy that a lot of them went in. As they went in, you start gaining more confidence and as your confidence builds, more putts go in, too."
This was just Matsuyama's day and a statement after Justin Thomas and Jason Kokrak tied the course record of 65 in the opening round.
Thomas followed up his course-record performance with a solid 69 to be 10 under through two rounds, while Kokrak (73) dropped into a tie for 21st at six under.
Former world number one and 2012 champion Rory McIlroy posted a second-round 67 as he improved 14 positions to 11th, alongside Kevin Tway (67), Tommy Fleetwood (66) and Kevin Kisner (68) at eight under.
Four-time major winner and US PGA Championship holder Brooks Koepka is seven shots off the pace following his 71, and he is joined by Northern Trust champion Patrick Reed (71).
Star names Jordan Spieth (71), Jason Day (71) and Justin Rose (73) are tied for 40th at three under, a shot better off than Tiger Woods and Dustin Johnson.
Woods – a two-time BMW Championship winner – is in serious danger of missing the trip to the Tour Championship after carding back-to-back 71s.
Only the top 30 players in the FedEx Cup standings will qualify and Woods is projected to finish 45th.