Rachels hit a 5-iron from 202 yards, 30 feet behind the flag at the par-5 finishing hole. He then conferred with his son and caddie, Sam, who told him the putt broke right.
I thought it broke left, Sammy Rachels said. I just decided to compromise. Like they always say, when in doubt, hit it straight.
Rachels, who uses a long putter, did just that, and then raised his arm in a triumphant gesture.
Rachels' 14-under 202 total gave him his second win on the Senior PGA Tour as he avoided a playoff by leaping over Floyd (64) and Tewell (66).
I did what every golfer wants an opportunity to do -- to make a 30-foot eagle putt to win it, Rachels said. Very, very cool.
Rachels, who won the BellSouth Senior Classic in June, joined Bruce Lietzke as the only rookies to win more than once on tour this year.
Rachels collected $195,000 for the victory, almost matching the $226,796 he earned over a 20-year career on the PGA Tour.
When the tournament's final group - John Mahaffey, Rachels and Allen Doyle - had five holes remaining, 11 golfers were within two strokes of the lead.
Then things really got interesting at the Silverado Country Club in Napa, Calif.
Rachels birdied No. 14 at the same time Floyd birdied 17, moving both to 12-under and into a tie with Mahaffey. Tewell then birdied 16 to create a four-way tie for the lead.
When Hale Irwin eagled No. 18, he was the leader in the clubhouse at 12-under. Floyd immediately grabbed the lead with his eighth birdie on No. 18 to go to 13-under.
Tewell tied him two groups later with a tap-in birdie on 18 after just missing an eagle with a superb chip off the green.
After missing a short birdie putt on 16, Mahaffey all but ended his chances with a bogey on No. 17. He had taken a one-stroke penalty at No. 8 when he accidentally dropped his ball on his mark on the green.
Full-field scores from The Transamerica