Thrill of chase a season-long ride for Martin Let's get one thing straight about Mark Martin: The 45-year-old NASCAR driver is no dark horse in the Chase for the Nextel Cup.  quot;You guys can call him a dark horse, but I don't, quot; said Jeff Gordon, who will be a 5-point leader over Hendrick Motorsports teammate Jimmie Johnson when NASCAR's inaugural 10-race playoff format is unveiled today in the ...