Lahiri, who set the course alight with a 61 on the second day and was tied sixth after the third round, had his most disappointing round on the final day as he carded a six-over 76 on the rock hard greens of Old White TPC.
The 67-61-71 on the first three days saw him find 72, 100 and 83 per cent greens in regulations and then it dropped to an abysmal 33 per cent on the final day.
As for putting, he missed a whole lot on the third and final days when the greens became rock hard and very difficult to putt.
He also dropped four places on the FedExCup rankings and is now 90th as he takes a week off before The Open.
Meanwhile, Korean-American Kevin won his first PGA Tour title since 2011. In the time since, he had six runner-up finishes and a host of other top 10s. He called those "A lot of heartbreaks".
On Sunday Na took control, almost from the outset, and fired a 64 that put him on road to a five-stroke victory over Kraft.
When he made a clutch 5-footer for par at the 14th hole to preserve his four-stroke advantage, Na admitted he could see the finish line clearly.
Kraft, who was tied for fifth a year ago in his debut at The Greenbrier was solo second yesterday with an even par 70.