The Pittsburgh Steelers upgraded backup quarterback Tommy Maddox from questionable to probable after Thursday's practice. By Sunday afternoon, the nine-year veteran, who has recovered remarkably quickly from a calf injury, could be upgraded to starter. With starter Ben Roethlisberger still slowed by a knee injury suffered late in the Monday night victory at San Diego, and unable to practice for a second straight day, the Steelers are strongly leaning toward starting Maddox against the Jacksonville Jaguars on Sunday at Heinz Field, sources confirmed to ESPN.com.