The championship match is scheduled at 8 a.m. Monday on the Dye course.
Both had entered a qualifying tournament Monday at the Country Club of Miami for the Royal Caribbean Classic, the season opener on the Champions Tour later this week at Crandon Park on Key Biscayne.
However, each was expected to compete here. The winner will earn $4,500, the runner-up $2,800, from the $52,130 prize fund.
In the semifinals Sunday, Vershure, 50, a two-time former champion, beat Chris Campbell, 48, of Vero Beach, 4-and-2, and Ralston, 53, defeated Steve Heckel, 56, of Carterville, Ill., 3-and-2.
Vershure, the head professional at Quaker Ridge Golf Club in Scarsdale, N.Y., has a chance to become the first three-time winner of the Match Play, which began in 1964. His previous titles were in 1990 and 1993. Both times, he beat Larry Rentz in the finals on the Champion course at PGA National in Palm Beach Gardens. Other previous two-time champions, all back-to-back, were Bob Brue, 1975-76; Lonnie Nielsen, 1987-88; and Gene George, 1996-97.
'I hit the ball more solid today than I have been all week,' Vershure said. 'I only missed two greens but I still didn't make anything,' carding just one birdie and two bogeys.
Vershure took a 3-up lead with pars at the third and fourth holes and a birdie at the seventh. After Campbell birdied the eighth, Vershure won the ninth, 10th and 11th holes with pars for a 5-up lead.
But after Campbell, head professional at Vista Plantation, won the 14th and 15th with birdies, he bogied the 16th and the match was over. 'I'm just disappointed I didn't play as well today as I have been this week,' Campbell said.
Ralston birdied the first and fourth holes for a 2-up lead before Heckel rallied to tie with birdies at Nos. 5 and 6. Ralston went in front again with birdie at the eighth and saved par at the ninth moments before Heckel lipped out his par putt.
'The ninth hole was huge,' said Heckel, pro-owner at Crab Orchard Golf Club. 'He's 15 yards longer off the tee than I am and some of those holes were just too long for me. He was hitting 4-irons and I was hitting 4-woods.'
With the lead at the turn, Ralston pulled away by winning the 13th and 15th holes with pars.
'This is the first time I've played in the PGA Match Play and I didn't decide to play until five minutes before the deadline' Heckel added. 'I usually have members and friends down this time of year and play golf with them. But I like match play. I've won the Gateway PGA Section Match Play three times.'
The Match Play is the last of six national championships staged here annually by the PGA of America. The PGA Winter Tournament Program is co-sponsored by Reebok Golf and the Greg Norman Collection.
Sunday's semifinal results:
Bob Ralston, Little Rock, Ark., d. Steve Heckel, Carterville, Ill., 3-and-2.
Rick Vershure, Armonk, N.Y., d. Chris Campbell, Vero Beach, 4-and-2.
Finals, 8 a.m., Ralston vs. Vershure.