Simpson had sole possession of the lead late in the round, before Stenson caught him during his birdie binge on the back nine.
Simpson, Kevin Na and Ollie Schniederjans were tied for second. "I've always loved playing close to home".
Schniederjans - a 24-year-old, third-year pro from Georgia Tech - is chasing his first victory on tour and his fifth top-10 finish of the year.
But the 2006 US Open victor fought back with two rounds of 66 to get inside the top 25 then turned on an exhibition over the opening nine holes of the final day.
Another subplot was the push by several players to qualify for the playoffs that start on Thursday at The Northern Trust for the top 125 players on the points list. He moved to 23rd after starting the week at 75th.
"I missed at least 5-6 putts inside 10 feet and some of them were inside six feet, so it could have been way better, even though 65 is not all that bad", said Lahiri.
Blair was right on the cut line for the 125th and final spot for status in next season's PGA Tour going into the final round of the Wydham Championship Sunday.
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Sources also revealed that the broadcast will be pre recorded as the president is not fit enough to do a live broadcast. The President who is said to have departed London this morning is expected to arrive at about 3pm this afternoon.
Stenson, the highest-ranked golfer in the field at ninth in the world, carded birdies on three of four holes during one stretch as he finished on the front side. "I still managed to produce some good stuff".
Martin Flores and Ben Crane aced the par-3 16th while Roberto Castro aced the third hole. "He's a little anxious to get out and start getting some air time I think next week already".
"Any time you're within two or three of the lead, you know you've got a good chance", Simpson said.
Steven Bowditch is 62nd after he continued to slip after an encouraging start while Aaron Baddeley and Stuart Appleby who both made the cut will not make the second cut and will finish 75th this week.
Siem was cruising in the final, three up at the turn and two up with five holes to play, but Otaegui produced an astonishing fightback to win 2&1. According to the PGA Tour Media Twitter account, the pro also made an albatross at the 2010 Sanderson Farms Championship.
"It was a very hard thing to do and I guess what the situation proved to me is how much I wanted to still be here".
Stenson began the day in second place overall and kept himself firmly in contention with a round of 66, dropping a shot on the 18th but managing five birdies. "I'm certainly hungry to win golf tournaments".