Hideki Matsuyama shot a 6-under 64 to hold a five-stroke lead heading into the final round of the FedEx St. Jude Championship.
Denny McCarthy, who was sharing the middle lead with Matsuyama, is now tied for sixth place, eight strokes behind, after adding four bogeys to his first birdie of the round.
Sam Burns was behind with just five pars on his way to a 70 and a broken driver, while world number one Scotty Scheffler also fell off the pace with a 69.
The top 50 players from this event will advance to next week's BMW Championship and all $20 million events next year.
Viktor Hovland made significant progress, shooting a third-round 66 to finish in third place, six strokes behind Matsuyama.
But Jordan Spieth's season was effectively over when he recorded two double-bogeys on his way to a 74, leaving him 69th in the field of 70.
Will Zalatoris entered the postseason ranked 49th and shot 67 on Saturday to tie McCarthy for sixth place. He is now all but certain to finish in the top 50.
Among those who are likely to advance to Sunday's final round are Justin Rose and Adam Scott. Rose, currently ninth at TPC Southwind in Memphis, is 55th in the FedEx Cup, while Scott, 25th, is 46th.
All PGA Tour events will be broadcast live on Sky Sports, with coverage of the FedEx St. Jude Championship continuing at 4pm. Sky Sports Golf On Sunday.
Watch the entire FedExCup Playoff live on Sky Sports Golf. Sky Sports+ Officially launched and integrated into Sky TV, streaming service NOW and the Sky Sports app, Sky Sports customers will be able to watch more than 50% more live sport at no extra cost this year. Find out more here.
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