Gilder shot a 4-under 67 on Sunday to win his first Senior PGA Tour title, while Nicklaus' hopes for his first victory since 1996 faded quickly in a round of 75.
"Of course it's disappointing," said Nicklaus, who wound up tied for 20th. "I felt good this morning, I felt composed and felt very confident about what I was going to do."
Gilder had an 8-under 205 total for a three-stroke victory over 2000 winner Bruce Fleisher, Gil Morgan, Bobby Walzel and Ray Floyd.
It was Glider's first win since the PGA Tour's 1983 Phoenix Open.
"That was a long time ago," Gilder said. "When you haven't won for that long, you wonder a little bit if it will happen again."
Gilder's short game was solid. He made three birdie putts of at least 16 feet.
"It carried me through," Gilder said. "It gives you a lot of confidence when you know you can putt and chip."
Allen Doyle, Larry Nelson and Christy O' Connor Jr. tied for sixth at 209. Hale Irwin, who started the round with a two-stroke advantage, shot a 74 to tie for ninth at 210.
Nicklaus hit 14 greens on the TPC at Tampa Bay course, considered one of the toughest on the senior circuit. But his putter deserted the first round co-leader as he missed five makable birdie putts on the front nine.
"It was just one of those days. I felt like I played pretty well," Nicklaus said. "If I go out on the last round of a tournament and hit 14 greens, I would think I would come up with a pretty good score and I didn't do it."
"As the day went on today, I just kept not making anything I needed to make."
Gilder earned $210,000. His biggest previous paycheck, $72,000, came for winning the 1982 Westchester Classic.
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