Is plain old fantasy football not time-wasting enough for you? A new twist promises more addictiveness--and is even more nerdy. This week a Silicon Valley start-up called Protrade (protrade.com) is launching an "athlete market" that merges the high-pressure action of stock-market trading with the skills of sports prognostication. The site is like a brokerage house where you buy and sell players. Their value fluctuates according to complicated calculations that supposedly track an athlete's feats to the value he brings to the team. (The secret sauce is a "Moneyball" -style formula.) If you buy shares in a blue-chip stock like Peyton Manning, you can expect regular dividends based on his performance--and if you take a chance on a rookie like Ryan Moats, you'll make a killing if he gets the ball and runs with it. Participants compete in various "challenges" (some free, others requiring a buy-in); the winner is the one whose portfolio grows the most. Prizes range from signed Ben Roethlisberger footballs to cash. The big thrills in Protrade will come at game time, when its Big Board-style Web site will turn users into fantasy-sports day traders, as share prices rise with every first-down catch and fall with each fumble. (If your QB is hurt, it's Black Sunday.) Protrade plans to add basketball and baseball players to its marketplace, to the consternation of sports widows everywhere.