RON SHELTON MAY BE THE ONLY GUY in Hollywood who makes sports movies in which winning isn't everything. In Tin Cup, the maker of ""Bull Durham,'' ""White Men Can't Jump'' and ""Cobb'' creates a romantic comedy around the game of golf, and gives us a hero whose motto is the hoariest post-Rocky emblem of them all: go for it. But you can trust Shelton to tweak the clich. By ""going for it'' time after stupid time, Roy (Tin Cup) McAvoy (Kevin Costner) has ended up as a golfing instructor at an armadillo-infested driving range in the west Texas town of Salome, rather than a well-heeled pro on the golf circuit like his old rival David Simms (Don Johnson). Roy never plays it safe, and it's cost him.
Besides, he's more than a little in love with his own boozy, grandiloquent self-destructiveness. He's good at failure: he can be a charming local legend without the responsibility of accomplishment. Then he meets Dr. Molly Griswold (Rene Russo), a long-legged psychotherapist who comes to him for a lesson, and suddenly he has a reason to go for it big time. He wants to win her; when he finds out she's already attached to the smarmy Simms, he wants her so bad he's roused to compete for the U.S. Open.
The good news about the amiable but only partly satisfying ""Tin Cup'' is that it frees Kevin Costner from playing a monument and restores to us the loose, sparkling comic actor he used to be. His sly, ardent, funny-sexy performance keeps this comedy humming, and he's backed up beautifully by Cheech Marin as Romeo, Roy's buddy-guru-caddie. The not-so-good news is that Russo's flustered, ditsy doctor doesn't hold up her end of the romantic bargain. Russo, who sizzled with Clint Eastwood in ""In the Line of Fire,'' never gets a handle on her character, in part because Shelton and co-writer John Norville haven't either. Where Roy seems flesh and tainted blood, Molly seems pieced together from brittle, defensive tics borrowed from a hundred other romantic comedies. But if you can overlook the missing chemistry at the heart of ""Tin Cup,'' there are lots of pungent pleasures along the way to the final green, where Shelton, with his usual contrarian wit, turns the convention of happy sports-movie endings on its head and still manages to make you happy.