When San Francisco's concussion-plagued star Steve Young wisely decided to retire rather than risk further injury in Denver, he left the Broncos with the same problem they've faced since May 1999 -- how to replace a legendary quarterback and team leader with a mere mortal. In the absence of John Elway, head coach Mike Shanahan will turn to third-year man Brian Griese, who's had growing pains on the field and in the dressing room. Can he throw long? Maybe: Bronco mini-campers say Bob Griese's boy is now ready for prime time. Failing that, Gus Frerotte, late of Washington and Detroit, will get the call. Can anyone here say Bubby Brister?