This film starts off like a romantic comedy with Kevin Costner playing a talented but decadent golfer trying to gain the affection of a flustered, psychologist played by Rene Russo. Following style, he sets out to enter the US Open to garner her respect. But once he gets in, the film loses it's original direction. It seals up the romantic drama pretty much once the Open starts and becomes much more focused on the golf. This isn't really a criticism, certainly not if your a golf fan, but more of an observation. I can't help but find that the intensity and excitement it tries to generate is something that simply doesn't exist in the game of golf.
Unlike films like, The Hustler, where you don't need to understand or even like the sport to appreciate the film, Tin Cup doesn't manage to pull off that type of drama that transcends environment.
Costner is well cast in this part and probably the only reason its watchable. The sport aspect isn't dramatic and the comedy isn't funny enough to construct anything memorable.