'I didn't think I realistically had a chance to win unless I posted 8- or 9-under today,' said Hensby, who earned $81,000 for the win. 'My goal was to play good and try to shoot 5- or 6-under and hopefully finish in the top-10.'
Johnson posted a 7-under 65 to join Hensby in the playoff. Tom Carter bogeyed the 17th but birdied the 18th to finish one shot out of the extra session at 19-under-par 269.
Hensby birdied the par-five 18th to get to 20-under and take the clubhouse lead. Johnson, playing four groups behind Hensby, ran off three straight birdies from the 14th to climb to minus-18. He later eagled the 18th to tie Hensby for the lead.
When those two players returned to the 537-yard 18th for the playoff, both players hit their drives down the fairway. Both players knocked their second shot greenside.
Hensby nearly holed his chip for eagle but it just stayed out of the cup. Johnson left his shot 10 feet from the pin, just off the edge of the green. He rolled a putt close to hole, but his birdie try did not fall and the title was Hensby's.
'I probably hit two better shots in the playoff than I did in regulation,' said Johnson. 'The execution was perfect. One bounce here, one bounce there. It's a funny game.'
The 32-year-old Hensby began the day five shots behind the leaders at The Dominion Club. He quickly climbed the leaderboard with an eagle at the second, then he drained a birdie on the par-five fourth. The birdie at four touched off a run of three straight birdies that got Hensby to 16-under par.
'I was five-under after six holes and when I looked at the leaderboard I was still in fifth place,' Hensby said. 'I'm thinking, 'what the heck is going on here with the scores so low?' From there, I knew I needed to make a lot more birdies.'
After five straight pars, Hensby birdied the 12th, then sank back-to-back birdies from the 14th to get to minus-19. He also birdied 18 to take the clubhouse lead.
Johnson rolled in three birdies on the front side that got him to minus-16. However he dropped a shot at the par-five 12th to halt his momentum.
Johnson, who won the Rheem Classic earlier this year, converted three consecutive birdies from the 14th before an eagle on the 18th got him into the playoff.
'I was pretty proud of myself for not getting distracted after I heard that on nine,' said Johnson, in reference to learning his close friend Ben Curtis had won the British Open. 'I was close to getting emotional myself. Winning the British couldn't have happened to a nicer guy.'
Daniel Chopra carded a six-under 66 Sunday to finish in a tie for fourth. He shared fourth place with Sonny Skinner and Bo Van Pelt at 18-under-par 270. Tripp Isenhour ended up one shot behind that trio at minus-17.