The Chiefs claimed Orton off waivers from the Denver Broncos on November 24.
Tim Tebow's ascent in Denver led to the unsuspected release of Orton, who started 33 games for the Broncos over the last three seasons. In his first five games this year, Orton completed 91-of-155 passes for 979 yards, eight touchdowns and seven interceptions, but Denver went just 1-4 over that span.
Orton made his Chiefs debut on the first play of the second quarter against the Chicago Bears on Sunday, but left the game after dislocating his right index finger. Orton's follow-through on an attempted pass caught the top of Major Wright's helmet, who was blitzing on the play.
The 28-year-old Pittsburgh product has thrown for 601 yards with a touchdown and six interceptions during Cassel's absence.
The Chiefs sit at 5-7 on the season and trail the division-leading Broncos and Raiders by two games.