Mike Riordan has made the major decisions of adult life by playing the percentages. So he didn't need Jimmy the Greek to tell him that the odds were 100 to 1 against his continuing in pro basketball this season.

"I've reached the point of no return," he said. "Unless someone pops up and tells me that I will be an integral part of a team this year, my playing days are over. I don't see anyone coming after me now."

Riordan's probable retirement five days before the Bullet veterans report to training camp won't be heady news around the league. But his departure marks the end of an era in the NBA, for he is the last of the true blue-collar players, a rough diamond in the midst of sparking gems.

He is the last of a special kind of pro who cared more about fast breaks than investment reports and who relied more on cunning and guts and sticking that wonderful lantern jaw into the right places than on natural talent.

When he was drafted by the Knicks on the 12th round 10 years ago (behind notables as Bubba Smith, Randy Matson and Ron Widby), he covered the percentages by lining up a graduate assistant's job at his alma mater, Providence. It seemed thought his chances of making the pros ranked below slim and none.

Now the percentages have told him to plot out a future in something other than the NBA. That's why he opened a bar-restaurant, Riordan's Saloon, last spring in the waterfront area of this capital city.

The place used to be called the Upper Crust, a name that still causes Riordan some embarrassment. "Imagine," he says, "me being in a place that had a name like that."

Riordan's establishment reflects his approach to life. It is comfortable and unpretentious. He sells green T-shirt with "Riordan's Saloon" imprinted on them and his idea of a dress code is not having one. The menu is simple, featuring sea food and "good old American sandwiches." But there are frest flowers on every table.

"This is the one major business investment I've made," said Riordan. "I've always tried to remember, where I came from, even during the high points of my career. I've seen too many players leave the game not knowing what to do; it must be the biggest problem in the league right now.

"I never had any illusions about my talents. I never expected my career to continue for very long. I just got on the train and rode it for as long as I could. I never had the luxury of talent like a lot of players, so I could always see the end."

For him, the end has come sooner than expected. At age 32, he still feels he can perform capably, maybe for another year or so. But he doesn't want to spend another season like the last one, sitting at the end of the branch, playing ou the final minutes of lopsided games.

It is remarkable Riordan has laster this long. At 6-foot-4, he was always at an in-between height for the pros. He was never quite strong enough, never quite efficient enough to remain secure in his job, especially when playing alongside a pure talent like Elvin Hayes. Even when he was on top of his game, the Bullets always were searching for a replacement. When he stumbled, the list of challengers to move him out grew longer: Weatherspoon, Hobinson, Grevey and, finally, Dandridge and Ballard.

But he shows no bitterness toward the Bullets. Instead, he says the team officials did as much as he could expect when they told him earlier this summer that they probably couldn't use his services anymore.

"They were honest and they let me know where I stood before training camp began," he said. "It wouldn't have been unfair to take me to camp and then cut me the last week. That would take away what zest I had left for the game."

It was that zest that separated Riordan from most players and made him the darling of Capitol Centre fans.

He never stopped running and he never stopped playing the hand-checking, aggressive defense that so iritated opponents. He loved the game so much that his season really never ended. It would just shift from the cavernous indoor areas to some summer outdoor court, where he could keep his legs in shape and practice that moonball jump shot.

He always looked our of place on the court. His uniform never seemed to fit and his funny running form made him look like all knees and elbows.

For while, he was one of the NBA's prototype small forwards, a position he learned after coming to the Bullets in a trade withthe Knicks six years ago. It was during three wonderful years, from 1972 through 1975, that he scored so many baskets at the end of Wes Unseld's blazing outlet passes.

It was also at the end of that era, in the last game of the disastrous 1975 playoff final against Golden State that Riordan had his bleakest moment with the team. Unfortunately he said, as he recalled the incident while sitting at his restaurant's bar with an apron over his blue jeans, "some people never can forget it."

With Rick Barry getting away with what Riordan said "was murder with the refs, getting them to call cheap fould." Bullet coach K. C. Jones, his team down 3-0 in the series, asked Riordan to give Barry one or two hard checks "to show the refs what a foul really is."

After the second such collision with Barry, a scuffle erupted. Warrior Coach Al Attles was ejected and Riordan's image as a mugger was established. Golden State fans still were booing him two years later and he thought I was trying to maim him or cheap-shot him. I wasn't. I would never do that, even if they wanted me to and fined me if I didn't."

Memories of that day, however, are offset in Riordan's mind by a horde of brighter times, beginning with his school days in Great Neck, Long Island.

"I grew up in a blue-collar neighborhood," he said. "Most of the kids went to the service or the cops or fire. A small percentage went to college."

He became part of that small percentage because his parents, who had immigrated from Ireland, pushed him in that direction. He pushed himself into basketball, perfecting his skills nearby city playgrounds and then gaining some notoriety as a 6-foot-2 center on his Catholic high school team.

When he looked toward college, the best offer came from Providence, a school he had grown to love by watching Holiday Festival and NIT games in the old Madison Square Gardon. But Providence hedged its bet, giving him only a partial athletic scholarship. It wasn't the last time the experts waivered when assessing Riordan's ability.

"I came in with Jimmy Walker," Riordan remembered. "When we left, he was the first player chosen in the draft and I barely got picked.I tried out for the Knicks only after I knew I had the graduate assistant's job at Providence I thought I had a chance but I wanted to be safe."

The Knicks liked what they saw enough to farm him out to the Easter League. By the next season, he was on the varsity, playing the role of a foul giver for part of the season before moving in as No. 3 guard. In that position, he helped contribute to the Knicks' championship season of 1970.

"Being a part of that team remains the highlight of my basketball career," he said. "There is nothing like winning a title. It creates a relationship among the players that is hard to describe."

Which is why he took the trade to the Bullets so hard at first. The Knicks had always been his favorite team, he was a New York native and he was uncertain of his future. But when the Bullets traded away Jack Marin, Riordan found a second career at forward.

He also brought his refreshing manner in a team that responded to his devillish personality be eventually making him player representative. He contributed by helping to bread the squad dress code.

Clothes and Riordan have never gotten along. He hates ties, feels at home in jeans and relishes the fact "I never need a red cap when I go on road trips. Never had so many suitcases I couldn't handle them myself."

Although his nickname. Bags came from his knick days and a postgame ceremony that included a slightly off-color awarding of game balls for the worst shot of the night, it eventually grew to be associated with the few suitcases he took on trips.

But when he joined the Bullets, he faced the possibility of needing more clothes. "We still had a rule that you had to wear a coat ad tie anytime you appeared in public on trips," he said. "We had some new players on the team and we all told (coach) Gene Shue we didn't own a tie.

"So he saw the handwritten on the wall and dropped the rule. I guess I've never been one for Superfly outfits and three-piece suits."

Nor has he been one for watches ("I don't like to be on schedules") or gaudy symbols of his status as an NBA star. He'd much rather be a jokester, as any of his teammates will attest.

Once, he and Unseld attended the film," Exorcist." As soon as he saw that Unseld was wrapped up in the gory action. Riordan excusted himself to get some popcorn.

"I really into the movie," said Unseld. "All of sudden I feel this hot breath on my neck and these weird sounds. It scared the hell out of me. I should have known it was him."

Riordan talked Unseld into drinking his first beer - "I threw it up all over a hotel lobby" - and constantly tried to make Bullet players believe the most outrageous things. "It's hard for me to take things seriously," he said.

Except when it comes to those matters close to his wallet. Although it might seem he would be more comfortable doing his own contract negotiating with teams, Riordan signed early in his career with an agent.

"I learned quickly that the business aspect is so important," he said. "I wanted someone who could go in and push my worth, who knew what they were doing."

Riordan had a unique first choice for his agent: Bill Bradley, who was then in his prime with the Knicks.

"Why not?" asked Riordan. "When the team starts saying that you aren't worth a crap, who would be better to explain to them your strengths than a guy who had to guard you?

"I was perfectly serious. I talked to him about it and you could see his eyes sparkle. But he finally decided it would be a conflict of interest."

Now the days when he needs an agent are just about over. He sees himself as a restaurant owner "for a number of years" because he likes the job, even if it means working five long shirts a week.

"I've worked at every phase of the job, from cooking to tending tables," he said. "I was a player coach at first but now I'm full-time coach here. I guess people expect me to be out front, gladhanding them all the time, but I've got too much else to do."

But won't you miss baskerball? Hell, yes. I love the game, it's my blood. But, well, the percentages just aren't there any more, so why right them?"