It was a fairytale finish to the season for 23-year-old Schauffele, who barely qualified for the 30-man Tour Championship field.
Sergio Garcia has four birdies on a bogey-free round so far.
Thomas recalled how he started the 2016-17 season on a strong note with his second win at the CIMB Classic, which is the only PGA TOUR event staged in Southeast Asia.
Thomas was battling comers from all sides on Sunday, too. It caps off what will surely be a rookie-of-the-year-worthy season, one that featured his two victories, three top-10s, 10 top-25s and more than $6 million in total earnings. Because he put himself in such a good position over the first three days, closing came a little easier.
He also could have said "life-changing", which is how Thomas repeatedly described his own five-victory season, which included his first major title. "It's hard at first because as a competitor, you're made you didn't win the tournament". "To realize you can play so well for a whole year is so gratifying". 2017 has been quite a year for Thomas and I wouldn't be surprised if it ends with a player of the year award. It was a gruelling day for sure and nerve racking.
If he seals the deal this morning, he could win the tournament, the FedEx Cup title and the combined US$11.58 million (S$15.6m) jackpot which allow him to buy a lot of baby gifts.
At Alabama, Thomas was the National Player of the Year in 2012 and a member of the Crimson Tide's national-championship team in 2013. In terms of actual golf game, my short game helped me out a lot. "I need to work on making those waves smaller", he said. "I was glad that it paid off". After finding the putting surface with his third shot Thomas hit what looked to be a ideal putt from 24-feet before it broke hard left in the final few rolls to miss on the low side.
Schauffele, the first rookie to win the Tour Championship, described his whirlwind summer as "unreal".
"If you told someone that going into a tournament, you're like, Yeah, I'm just trying to finish better than 45th, it's like why are you going?" That's why we play. He's the future of golf along with Jordan Spieth, Rory McIlroy, Jon Rahm and a handful of other 20-somethings.
By then - if not next year - a new format should be in place that either allows the Tour Championship victor to be crowned FedEx Cup champion, too, or leads to some sort of one-day shootout for the big prize. In 25 worldwide starts, he had a dozen top-10s and for good measure also had a 59 at the Sony Open in Hawaii and a 63 in the U.S. Open.