He'd walk off with the win instead.
Lehman eagled the par-5 eighth and played a 10-hole stretch in 7 under before dropping a stroke on the par-4 18th. He was swinging without pressure when he stood over his shot in the light rough to the right of the 18th fairway, and hit the flawless shot to finish off the win.
Johnson shot a four-under 66 to finish at 19 under for his second PGA Tour victory this year and 18th of his career to move back to the top of the world golf rankings.
Dustin Johnson already had his 18th career PGA Tour victory in his grasp, but he made a decision to end his day with an exclamation point anyway.More news: Paul raccoon reaches roof after death-defying climb up downtown tower
"Winning this week I think is a bigger confidence booster than being No. 1 in the world", Johnson said. Johnson tied Tiger Woods for the most wins since 2008 (18) and his second St. Jude win was his ninth since the beginning of 2016.
"I was a little flat starting the day - I couldn't really get anything going", Johnson explained.
But what we do know heading into the U.S. Open on Thursday is this: We know who not to bet against.
Johnson finished with the eagle, three birdies and a bogey on Sunday while co-overnight leader Andrew Putnam started the final round with a double bogey on his way to a 72.
Johnson was made aware of this on Sunday and shrugged it off, predictably.More news: Wonder Woman 2: Patty Jenkins teases return of key character
J.B. Holmes (67) was at 9 under.
Brooks Koepka, a week before defending his U.S. Open title, carded 69 to slip five strokes behind, while Phil Mickelson (70) fell six adrift.
At least until his final dramatic shot. He two-putted from 29 feet on the par-5 No. 3 and drained a 16-footer for birdie on No. 6.
On the 482-yard par-4 seventh hole, Thornberry reached the green in 2 and sunk a 20-foot putt for birdie.
"I've got a lot of control of my golf ball and that's what you're looking for going into any week but, yeah, especially going into tomorrow and then obviously next week".More news: Xbox shows off record number of games as it promises 'biggest year'
Johnson will be among the favourites to win the U.S. Open starting on Thursday at the Shinnecock Hills Golf Course in NY and he is confident of repeating his 2016 victory in the year's second major. He holed out from the right front bunker for birdie on the par-5 No. 16.