I f Clarence Darrow were around today, chances are he'd be a sports lawyer. With its constantly shifting playing field, groundbreaking decisions and high-profile clientele, it's just the kind of law that would have appealed to him. Sports law, sometimes described as "the Wild West" of jurisprudence, isn't for outlaws though. It's the province of a whole new breed of sports lawyers - often former amateur athletes themselves - whose shingles read "player agent." Johnnie Cochrane is one of the more famous of course. You may remember he made a name for himself during the O.J. Simpson trial. Cochrane's now a registered player agent with the National Basketball Association.