Patrick Cantlay and Jon Rahm produced some sublime golf at the Tour Championship on Friday, but the American holds a one-shot lead on 17-under-par at the halfway stage.
Cantlay, who began his week in pursuit of the FedEx Cup with a 3-under-par 67, played very calmly and consistently on the front nine by making eight pars and just one birdie.
The five-time PGA Tour winner then almost holed out from the fairway with his second shot at the 13th hole, but this birdie helped him to move to 15-under-par.
But Rahm matched Cantlay. Having made just the one birdie on the front nine as well, he made back-to-back birdies on the 12th and 13th holes to move just one behind his opponent, in what became a two-man showdown at East Lake Golf Club.
The World No. 1 made three fantastic birdies in his last three holes, and he almost holed his bunker shot on the final green for an eagle to draw level with Cantlay on 17-under-par.
The Spaniard settled for a 5-under-par 65 on Friday to sit on 16-under-par for the week. Cantlay crucially birdied his final two holes in Atlanta to shoot a 66, keeping Rahm at arm's length with a one-shot lead.
Both players have been mightily impressive in the final stages of the season. Rahm has made four consecutive top-10 finishes on the PGA Tour, while Cantlay thrillingly won the BMW Championship last week in Maryland.
Bryson DeChambeau, who Cantlay defeated in a six-hole playoff last week, is on 11-under-par for the tournament after carding a 3-under-par 67 in the second round.
The big-hitting American was 3-under-par for his round but he then made back-to-back bogeys at the 13th and 14th holes. Two birdies in his last two holes meant that he finished six shots behind Cantlay.
Justin Thomas is a further shot back in fourth place on 10-under-par, while there are five players in a tie for fifth on 9-under-par.