Schauffele, who led overnight and for much of the final round, failed with his 60-footer as he posted a 70, while US Open champion Clark’s 17-footer horseshoed around the hole and left him signing for a 69.
Asked what it was like to become the first player to win successive Players titles, Scheffler said: “It’s pretty special.
“It’s something you don’t get the opportunity to do very often. It’s tough enough to win one.”
He is the youngest player, at the age of 27, to win two titles – only Jack Nicklaus has won the event three times.
His eighth PGA Tour victory – which followed last week’s win at the Arnold Palmer Invitational – is all the more remarkable considering the pain he was in during Friday’s second round when he tweaked his neck while playing a shot.
He called for a physio who worked on the injury between holes and he was still in obvious discomfort during Saturday’s third round.
“I didn’t want to give up in the tournament,” said Scheffler, who collected $4.5m (£3.5m) from the $25m prize fund. “I did what I could to hang around until my neck got better and [on Sunday] it felt really good.”
And as much as Harman, Schauffele and Clark squandered their opportunities, Scheffler earned his historic victory with a stunning bogey-free final round as he matched the record comeback wins of Justin Leonard in 1998 and Henrik Stenson in 2009.
He had eradicated Schauffele’s lead by the ninth hole. A chip-in eagle two on the par-four fourth sparked the comeback and Scheffler followed that with three birdies in five holes to join Schauffele on 17 under.
But moments later Schauffele knocked in a birdie on seven to move one ahead.
That set the scene for a nerve-shredding back nine, with Scheffler, Schauffele and Clark taking or sharing the lead at various points.
While Scheffler posted birdies on the 11th, 12th and 16th holes, Schauffele and Clark were dropping shots.
Clark, who led by four strokes at the halfway stage of the tournament following two rounds of 67, bogeyed the 10th and 14th to drop to 17 under, while Schauffele bogeyed the 14th and 15th as he slipped to 18 under.
Meanwhile, Open champion Harman was quietly creeping up the leaderboard, with four birdies in five holes around the turn taking him to 18 under.
He rolled in another on the 15th but was unable to pick up another shot on the famously tough closing three holes.
Schauffele and Clark birdied the par-five 16th to move to 19 and 18 under respectively and played sensational tee shots to inside eight feet on the notoriously difficult par-three 17th ‘island hole’.
Schauffele missed his birdie putt. Clark holed. Both needed to birdie the last to match Scheffler. Both failed.
“When I went to bed last night, it’s not exactly how I envisioned walking off the 18th green,” said Schauffele, whose last victory was the 2022 Scottish Open.
“This sucks but I’ll lick my wounds and right back to it next week.”
