Schauffele, who entered the third round tied for eighth, shot a 5 under par to put himself in the final pairing with Casey.
Spieth entered the final event of the season leading the FedEx Cup point standings. He is 4 under par after a third round, with four birdies and four bogeys.
"Unfortunately, I'm not really in control of my own destiny at this point, but I'll go out tomorrow, try and shoot a really solid round of golf and then do some cheerleading," Spieth said. "That's kind of the plan."
For a change, Spieth will be trying to catch Casey. So much for those youngsters who have dominated the PGA Tour this year. Of the 47 events this year, 27 have been won by a golfer in their 20s. A total of 19 players have done all that winning. By stark contrast, just five golfers in their 40s have won this year.
"I still have great physical talent," Casey said. "So the age thing doesn't bother me. I don't see it as a handicap in any way. It would be cool to brag about it to the young guys. I don't think about it too much but, for me, the clock is ticking for sure."
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