Cleveland quarterbacks Brandon Weeden and Colt McCoy both have injured right shoulders, leaving Shurmur to give Lewis his first NFL start.
In fact, Lewis, who was signed by the St. Louis Rams in 2010 as an undrafted free agent, has yet to play in an NFL game. He will be going against the No. 1 defense in the NFL in the Steelers.
The Browns this week signed Josh Johnson, who will serve as backup to Lewis.
Shurmur also said rookie running back Trent Richardson, who has gained 950 yards this season, will miss Sunday's game because of a sprained ankle. Montario Hardesty will start in Richardson's place.
The Browns wrap up their 2012 season Sunday at Pittsburgh. Cleveland is 5-10 on the year and in fourth place in the AFC North. The Steelers (7-8) are in third.