"Semi-Tough," opening today at area theaters, is probably Michael Ritchie's slickest and most confident movie yet. Well supplied with both raunchy humor and star appeal, particularly in the person of Burt Reynolds, the film seems certain to become a crowd-pleaser.

Given a strong predisposition to enjoy Ritchie's style, Reynold's personality and the source material that brought the twain together - Dan Jenkins' delightful, idiomatic comic novel about the confessions of NFL star Billy Clyde Puckett during Super Bowl Week, published in 1972 - I wish I liked "Semi-Tough" more than I did. That is, I wish the movie adaptation were carried along by a sense of humor as personal, spontaneous, mischievous and uninhibited as the one that sustained the book for 200 episodic, anecdotal pages.

While retaining Jenkin's major characters and general outline - the movie scenario also leads up to the Super Bowl but encompasses the playoff period as well - Ritchie and screenwriter Walter Bernstein have attempted to remold the material into a conventionally plotted romantic comedy triangle.

Reynolds, as Billy Clyde, is faced with the sudden prospect of marriage between his closest friends, wide receiver Shake Tiller (Kris Kristofferson) and their mutual childhood sweetheart and supposedly platonic roommate, Barbara Jane Bookman (Jill Clapburgh).

Billy Clyde realizes that he's more than fraternally fond of Barbara Jane and begins a subtle campaign to smooth out Shake and sabotage the wedding, which replaces the big game as the comic and slapstick climax of the story.

At the same time the filmmakers have subordinated Jenkins' principal sources and targets of humor - professional athletes and the National Football League - to satirical episodes aimed at the consciousness movement, which is seen as exerting a special fascination upon the sporting world.

The plot alterations and shifts in comic emphasis aren't necessarily regrettable, and moviegoers who haven't read the book may be immune from disappointment. The fact remains, however, that the book asserted a comic originality and definition that the movie has submerged and never quite compensates for in terms of increased romantic gratification or freshly inventive and liberating ridicule at the expense of est, Rolfing, attack therepy and the other self-improvement disciplines it kids.

Although Ritchie's direction seems smoother than it's ever been, "Semi-Tough" also seems a more impersonal kind of commercial film comedy than Ritchie ever has made before. It doesn't get under your skin or start to diverge and ramify in unexpected ways, like "the Bad News Bears" and "Smile" and even the exceedingly streamlined, underwritten "Downhill Racer." It's profanely funny and visually attractive, yet also curiously perishable and forgetable, especially for an entertainment whose every effect seems carefully calculated.

Perhaps that's the hitch: The calculation may be too apparent to generate enough spontaneous enjoyment. The consciousness movement episdoes, for example, are not so funny as disdainful.

When Robert Preston, cast as Big Ed Bookman, Barbara Jane's oilman father, now identified as the owner of the team Bill Clyde and Shake play for as well, enters his office on his hands and knees, induliging his pet therapy of "Moeagencics" - evidently inspired by one of the quirks of the late H. L. Hunt - you expect to be amused, yet the effect is grotesque without being funny.

Bert Convy and Lotte Lenya do contribute amusing performances as Friedrich Bismark, founder of Bismark Energy Attack Training, and Clara Pelf, founder of the Pelf Institute of Muscular Harmony. However, one experiences the same uncomfortable sensation of waiting in vain for the sequences depicting their therapies to get rolling.

The Shake of the novel was an athlete with restless, far-out intellectual interests that finally made him a less satisfying suitor for down-to-earth Barbara Jane than down-to-earth Billy Clyde. The movie had lost the book's humorous perception of Shake as someone who's too hip for his homebody best friends.

Kristofferson's Shake is closer to the Ralph Bellamy characters in "The Awful Truth" and "His Girl Friday" - a nice square, perfectly pleasant to be around but out of the question as a serious romantic threat to the hero.

The fudging isn't necessary, because Reynolds and Clayburgh look wonderful together. They seem to harmonize in a way that would only be more apparent - and make their eventual recognition of being in love seem more appropriate - if Kristofferson had been able to impersonate the original, fast-moving, glamorously flaky Shake.

Reynolds does more with Billy Clyde's barely perceptible frustration and deadpan scheming than one would imagine possible. In "Smokey and the Bandit" he suggested a live action equivalent of the Roadrunner. In "Semi-Tough" he's more like a love-starved Wile E. Coyote, engaged in a superhuman and ultimately successful effort to hide his longing in order to get his heart's desire.