Mattison is a third-year guard who played at Iowa in college. At 6'3", 310 pounds, he appeared in two games as a rookie with the Baltimore Ravens in 2010. Last season, he played in eight more games with the Ravens before ending up with the Saint Louis Rams, where he started in four games.
In the previous week, the Chiefs offensive line -- especially in regards to the practice squad -- brought in lineman Rich Ranglin, released Junior Hemingway, then released Ranglin and brought back Hemingway. Joel Thorman at Arrowhead Pride speculates that Mattison's invite primarily revolves around needing another lineman for the practice squad.
The Chiefs (0-1) are currently preparing to travel to Buffalo to play the Bills (0-1) this Sunday.