The Bucs had to add another quarterback to the 53-man roster due to an injury to starter Josh McCown. McCown tore a ligament in his right thumb against the Falcons in Week 3. He is out for Sunday's game against the Steelers, and could miss more time.
Mike Glennon, who started 13 games for Tampa Bay last season, will start on Sunday.
Kafka was a fourth-round draft pick from Northwestern in 2010. His only NFL action came in 2011, when he threw 16 passes in four games.
- Dan Gartland