NASHVILLE, Tenn. -- Former Heisman Trophy winner Jason White ended his professional career Thursday, citing his weak knees. White, who had been competing for third quarterback with the Tennessee Titans, said he has the head and heart to play in the NFL, but not the knees. "It's always been a dream of mine, but certain things won't allow me to chase that dream," White said. "It's kind of out of my hands at this point." White won the Heisman in 2003 and led Oklahoma to back-to-back BCS title games. He is Oklahoma's career passing leader with 7,922 yards and in...