Scottie Scheffler maintained his lead at the Tour Championship at East Lake after 36 holes but Xander Schauffele's superb finish closed the gap considerably.
Scheffler, 25, the reigning Masters champion, began the day with a five-shot lead and at one stage during the second round that lead was as many as seven strokes.
However, Schauffele finished birdie-birdie-eagle to card a 7-under 63, taking him to 17-under par for the championship and only two behind Scheffler.
Scheffler carded a bogey-free 66 after opening the final event of the PGA Tour's FedEx Cup Playoffs with a 65. The winner of this tournament will take home $18million.
Related: Scottie Scheffler reveals TMI injury
He told the media: "I like being in positions where I'm able to win tournaments, and it's something I've grown more comfortable with over time.
"I played well with the lead at the Masters this year, and that was definitely a lot of pressure. This week is definitely a good amount of pressure, as well.
"But I've been playing well, and just hoping to do some more of that the next two days."
The low round of the day was provided by Max Homa with an 8-under 62. Homa fired five birdies on the front nine in Atlanta, picked up another stroke at No. 16 and finished with an eagle.
Homa said: "Sometimes the ball just wants to go in. But I do believe I've been putting good work in with the putter and it feels really good in my hands, and I deed feel today like freed up and just trying to, like I said before, just try and trust myself instead of trying to make the ball go in the hole.
"It doesn't ever listen, so I tried not to talk to it as much today and just roll it."
Elsewhere, Rory McIlroy is chasing his third FedEx Cup title. After one of the most psychopathic rounds we've seen from the Northern Irishman yesterday, he carded his second round of 3-under 67.
McIlroy is 10 strokes behind Scheffler and will need two really low rounds if he is going to force his way back into the championship.
Jon Rahm (63), Patrick Cantlay (66) and Sungjae Im round off the top-5.
Leaderboard after 36 holes:
Cantlay, Im -12
Homa, Hoge, Young -9