Three-putt bogeys at 16 and 18 quelled his momentum and Woods was left to wonder what could have been.
A flawless drive at the par-5 fifth left Woods in the center of the fairway, and he ripped a 237-yard iron shot to 13 feet for eagle and drained the putt.
Meanwhile, Woods was first in the field in strokes gained, tee to green; first in strokes gained, approach to the green; and first in proximity to the hole, with an average of 23 feet, 8 inches.
Tiger Woods was already charging in Round two of the Memorial Tournament when he sent the crowd into a frenzy with a hole-out eagle at the par-5 11th hole.
Patrick Cantlay, one of three players sharing second overnight, had four birdies in the first eight holes and was two shots ahead at the turn, but dropped three on the way home and finished 14 under.
For Woods, the last memory of his four rounds at Muirfield Village will be sublime ballstriking, the best in the field and better than anything he has produced going back to the first of his four back surgeries. He missed a 3-foot birdie putt on the ninth hole, and then missed a birdie putt from 4 feet on the par-5 15th.
However, DeChambeau rolled in a nine-footer on a similar line to the one he missed in regulation play, to take the title. Notes: Tiger Woods, a five-time Memorial victor, is playing for the first time since 2015.
"I want to play well in front of my family", he said.
It's the 24-year-old's second PGA Tour win, as the 2015 U.S. Amateur champion made his debut in the winner's circle at last year's John Deere Classic.
DeChambeau gained the advantage again as he followed another flawless three-wood with a much better approach to 12 feet, while An tugged his second towards the gallery before playing a sublime flop-shot to five feet to put the pressure on the American. "Had total control of what I was doing out there and just didn't finish it off".
Rory McIlroy made bogeys on both par 5s on the front nine as he tried to finish strong. Still, with the leaders making birdies, he may need some help to remain in contention heading into Sunday.
"I think I just (stunk) on it for a long time", Day said.
Niemann, 19, highlighted his round with a 50-foot eagle putt at the par-five seventh.
He finished with a 4-under-par 68, but much like Friday when he shot 67, he walked off disappointed rather than exuberant.