Justin Thomas set a new course record in the third round as he stormed to the top of the BMW Championship leaderboard.
Thomas carded an 11-under-par 61 to shatter the record at Medinah Country Club for a commanding six-stroke lead on Saturday.
Hideki Matsuyama had set the record on Friday, but his feat was eclipsed by 2017 FedEx Cup champion Thomas – who stole the show with two eagles and eight birdies.
Thomas birdied his opening five holes and had six through his first eight, before adding another two and a pair of eagles on the back nine.
The American is set to move top of the FedEx Cup standings as things stand, with Thomas 21 under after three rounds – ahead of Tony Finau (68) and Patrick Cantlay (68).
"I just hope the trend doesn't [continue] and someone else breaks [the course record] tomorrow," he said after his stellar round.
"It's just one of those freaky days where you get in the zone. I hit the ball pretty unbelievable. I didn't really — it's not like I made any long putts, I just hit it close to the hole and took advantage of some opportunities when I had them and got a couple good breaks."
Rory Sabbatini posted a five-under-par 67 to be fourth and seven shots adrift, while Jon Rahm (66) is a stroke further back heading into Sunday's decider.
Brandt Snedeker (67) highlights a trio of golfers tied for sixth (12 under) and Rickie Fowler (68), Kevin Kisner (69), Xander Schauffele (70) and Matsuyama (73) all sit ninth.
Former world number one and 2012 champion Rory McIlroy is 11 shots behind Thomas following his third-round 70, while Tiger Woods is three shots back.
Two-time FedEx Cup champion Woods climbed the leaderboard thanks a to a bogey-free 67, which left him in a tie for 31st.
Only the top 30 players in the FedEx Cup standings will advance to the Tour Championship and Woods – who is the defending champion – is projected to finish 40th.