On Thanksgiving day, the Buccaneers would lose to the Dallas Cowboys, after Gradkowski threw two interceptions and only completed 10 passes. The following week, he continued to falter as he threw three interceptions in a loss to his hometown Pittsburgh Steelers. His play would continue to decline as he would lose the next two games against the Atlanta Falcons and Chicago Bears and was also benched in the middle of both games. In the second quarter in Chicago, he was pulled for good in favor of Tim Rattay. He would not start again in 2006 as Rattay led a comeback, accounting for four touchdowns in the second half, whereas under Gradkowski the team had a streak of 10 scoreless quarters. He finished his rookie season completing 177-of-328 pass attempts for 1,661 yards and nine touchdowns and nine interceptions.