"When I bent down to get behind it to act like I was lining it up, I was trying to breathe," he said. "I couldn't feel my arms I was so nervous."
When the ball rolled in on the 16th hole at the TPC River Highlands, Watson had won the Travelers Championship for his first PGA Tour victory in his 122nd start.
He won the 20th playoff in tournament history over Scott Verplank and Corey Pavin, who exited after the first playoff hole (No. 18) when Watson and Verplank made birdie.
Watson, who shot a 4-under-par 66, qualified for the playoff at 14-under 266 along with Pavin (66) and Verplank (64).
But neither Verplank nor Pavin, the U.S. Ryder Cup captain, could take down Watson in the playoff.
Seconds after Watson's final putt, which earned him $1.08 million, he embraced his wife Angie and broke into tears.
"I cry all the time," Watson said after receiving the trophy. "Everybody has issues, but you know our family had some issues and my dad [Gerry] is battling cancer; and my wife, we had a scare, we thought she had a tumor in her brain. We got lucky with that one and now we're battling with my dad."
Watson, 31, wiped away tears.
"I've never had a [golf] lesson," he said. "My dad took me to the golf course when I was 6 years old and just told me he was going to be in the woods looking for his ball, so he just told me to take this 9-iron and beat it down the fairway.
"And now look at me. After beating a 9-iron on the fairway, coming from Bagdad, Florida. I never dreamed this."
His par putt ended one of the most memorable days since the tournament began in 1952 at Wethersfield Country Club.
Watson and Pavin trailed third-round leader Justin Rose by six shots going into Sunday. Verplank started eight shots back. Watson's come-from-behind victory was the largest on the PGA Tour this season. It also tied for the second best in tournament history with Billy Maxwell in 1961. Brad Faxon's seven-shot comeback in 2005 is No. 1.
That there was a playoff Sunday was fueled by the meltdown of Rose, who started the day three shots ahead of Ben Curtis. Rose shot a 75 (269) to tie Skip Kendall and Kevin Johnson for the second-highest score of the round. Tim Herron had an 83.
Curtis (73—270) fell back to a tie for 13th.
"It's hard to play golf when you feel like you're going to miss every putt from two feet," said Rose, who shot a 39 on the back nine to tie for ninth.
Verplank was the first to finish at 266. He made a 50-foot eagle putt at the par-5 13th and then holed a 45-foot sand shot for eagle 2 at 15.
Pavin made the playoff by curling in a 32-foot birdie putt at 17. He then made a 5-foot par putt at 18 to join Verplank.
It looked like Watson, who earlier had taken the lead in regulation at 15 under with a birdie at 16, might have lost his chance at a playoff on 17. He topped his second shot from a fairway bunker into the pond. He ended with a double bogey 6.