Sigel reached the par-5 18th hole at The National Golf Club of Kansas City tied with McCullough at 10-under par. Sigel landed in a greenside bunker with his second shot and blasted out to nine feet. He sank the putt then watched as McCullough, who played in the group behind, headed to 18.
McCullough pulled his drive into the rough at the 577-yard closing hole. He laid up close to 100 yards from the pin and knocked his third shot onto the fringe. McCullough left himself with 20 feet for the tie, but missed the putt to give Sigel the title.
'At 59, my time off gave me some time to reflect on all of the good things we have, not just Jay Sigel but the Champions Tour as well,' said Sigel, who pocketed $240,000 for the win. 'This was thrilling today and very surprising to say the least.'
The win was Sigel's eighth since joining the Champions Tour in 1994. He became the 12th different winner in 12 events so far in the 2003 Champions Tour schedule.
Vicente Fernandez, the overnight leader, carded a 3-under 69 Sunday and finished alone in third place at 9-under-par 207. Pat McDonald and Hale Irwin posted matching rounds of 4-under 68 on Sunday and shared fourth place at minus-six.
Sigel trailed Fernandez by two to start the round but quickly made up the difference. He drained an eight-foot birdie putt at one, a six-footer at two and a two-foot birdie putt at three to reach the top of the leaderboard.
After a par at the fourth, Sigel made a 12-foot birdie putt at the fifth. He closed the front nine with a nine-foot birdie putt at the eighth and nearly collected his sixth birdie on the front nine, but missed a four-footer at No. 9.
McCullough kept pace with five birdies and a bogey on his front side, but Sigel started to distance himself from McCullough. Sigel made a brilliant par save from the bunker at 11 and holed a 12-foot birdie putt at the 12th. He tallied another birdie at 13 and when McCullough muffed a chip at 12 and took bogey, Sigel's advantage reached four.
Things got interesting later on the back nine. Sigel dropped a shot at the par-5 15th and McCullough did his part to make up the gap. McCullough tapped in a short birdie putt at 13, holed a 15-foot birdie at 14 and two-putted the par-5 15th green.
That last birdie tied the two until Sigel birdied 18 for the title. In the process, Sigel became the tour's oldest winner in 2003 at the age of 59.
'I'm thrilled with my score,' said Sigel, who won back-to-back U.S. Amateurs in 1982-83. 'I felt comfortable today starting out and thought I might shoot a good score. I hit a lot of shots at the pin. I couldn't have played a better round.'
McCullough, meanwhile, notched his third top-six finish of 2003.
'I'm exhausted mentally. I congratulate Kansas City and Jay Sigel,' said McCullough. 'It seemed like every time I made birdie, it was to catch up. It was Jay's turn to win. This event got a good winner.'
Fuzzy Zoeller fired a 6-under 66 and shared sixth place with Tom Jenkins (69), Allen Doyle (71) and Des Smyth (71). The group finished the tournament at 5-under-par 211.
Tom Watson, the course designer, tied for 10th with Jerry McGee, John Jacobs and James Mason at minus-4.