Snedeker, who began the final round with a wafer-thin one-shot cushion atop the leaderboard, could not be nudged from his perch all day, carding a two-under 70 to collect his sixth career US Tour win and second of the season.
While the margin of victory appeared comfortable, Snedeker's three-shot win over Johnson (70), world number six Matt Kuchar (71), William McGirt (68) and Jason Bohn (71) was not without considerable suspense.
Level with Johnson with three holes to play, Snedeker was suddenly gifted breathing space when Johnson botched the par four 17th, carding a triple-bogey seven to leave the FedExCup champion two clear of his nearest challenger.
Snedeker then birdied the 16th and coolly sealed the victory by parring his final two holes for a winning total of 16-under 272.
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