According to a league source, the Dolphins have joined the discussion with the Packers about acquiring Walker. The Broncos have considered acquiring Walker since last month, when coach Mike Shanahan made informal inquiries around the league, including to former Packers coach Mike Sherman, now on the coaching staff of the Houston Texans. Walker, who publicly has threatened to retire instead of again playing for the Packers, is under contract for the 2006 season. He is in Tallahassee, Fla., attending classes at Florida State University, where he also played for the Seminoles.