4. Tommy Maddox
Tommy Maddox joined the Steelers in 2001 after his MVP performance in the first iteration of the XFL. Maddox backed up Kordell Stewart and predominantly held the clipboard as the Steelers finished 13-3, falling just short of the Super Bowl against the eventual dynastic champion New England Patriots.
The next season, Maddox would see more opportunities as head coach Bill Cowher pulled on the always-short leash of Stewart in Week 4. Maddox led a comeback victory against the Cleveland Browns and was promptly named the starter. The Steelers were 7-3-1 under Maddox that season, missing two games due to injury.
That season's comeback player of the year had one more comeback against the Browns in him during the playoffs, rallying the Steelers from a 24-7 deficit on the back of 367 yards and three touchdowns.
The following season didn't see the same magic with Maddox as the full-time starter. The Steelers went 6-10, putting the team in position to draft Ben Roethlisberger in the 2004 NFL Draft. We all know how that story resulted for Maddox, as he left the Week 2 contest against the Ravens injured, opening the door for Roethlisberger to win 15 games. Maddox started the Week 16 game against Buffalo to help Pittsburgh keep its winning streak alive.
Maddox backed up Roethlisberger for one more season, stepping in for the injured starter, albeit in two losses that jeopardized the Steelers' playoff chances. Of course, those Steelers went on to win the franchise's fifth Super Bowl championship.