No one does unless it's someone with the kind of long history of dominance Mickelson has, the kind of resume that even at the age of 47 makes his name closing in on you on the leaderboard a tight fix and a testing moment for an apple-cheeked 24-year-old like Thomas.
Thomas finished at 17-under. He won the PGA Championship in August and now has five, five! wins this season.
Spieth had started birdie, eagle, birdie, birdie -but he couldn't keep it going, dropping a shot at the 14th and another at the last when he needed an eagle to tie. But Thomas held strong. Needing an eagle on the par-5 18th to stay in the game, he pushed a 4-iron into a tough lie in the bunker, blasted over the green, and closed with a bogey for a 67.
The eyes, the ears, the cameras were on noted friends Jordan Spieth and Justin Thomas. He bogeyed the next hole and when Thomas parred 14 he had the lead for good, not only refusing to relent but expanding on it with a birdie on 15 to go 2-up and effectively close the show.
"It was a great week because I felt like I didn't have my best stuff at the start of the week, and that's just something I've gotten so much better at", Thomas said.
Spieth and Thomas are friends and have been competing against each other seemingly for forever.
Spieth's self-destruction at the Dell came one week after he blew a five-stroke lead in the final round and lost to Dustin Johnson in a playoff at The Northern Trust to open the postseason.
"I could have easily made pars on all those holes".
Then the top 30 players following the BMW Championship will qualify for the Tour Championship at East Lake Golf Club in Atlanta, beginning Sept 21. "I have two more opportunities to win", Thomas said.
Leishman faltered early on the back nine. He also birdied the seventh to be 6 under on his round at that point. Though he escaped with a bogey after a 14-foot-8-inch putt found bottom, the groove he had enjoyed over the past 48 hours was fading fast. The 30th-ranked Aussie rolled in six birdies on the day and has played his past 28 holes bogey-free.
Leishman finished third at 13 under after firing a one-under 70 on Monday, while it was a second straight runner-up finish for Spieth.
Stewart Cink closed with a 68 to finish 12th, more than enough for him to advance to the third FedEx Cup playoff event outside Chicago for the first time in seven years.
SHOT OF THE DAY: This incredible approach from the rough at No. 13 led to a birdie and was the catalyst to Thomas' win. Neither could Jon Rahm or Paul Casey. They are competitors and rivals for whom winning remains paramount but in their case it seems, it is more like a rivalry between brothers than between warriors.
Although Spieth is Thomas' contemporary, he has shot nearly immediately into the consciousness of golf fans, winning three majors, 11 tournaments, the 2015 FedEx Cup championship and Tour Player of the Year.