Mathis, 35, has been in the league’s concussion protocol in recent days, but it appears as though his situation is serious enough for the Lions to hold him out for the remainder of the year.
He signed a two-year, $3.5 million contract that included a $750,000 signing bonus with the Lions back in March. Mathis will make a base salary of $1 million for the 2015 season and another $1 million in 2016.
Mathis’ 2015 season ends with him appearing in seven games and recording 30 tackles, one interception, a forced fumble and four pass defenses.
Butler, 28, is a former fifth-round pick of the Steelers back in 2010. Since then, Butler has played for a number of teams including the Cardinals, Redskins, Bills, Chargers, Buccaneers and most recent for the Lions.
Detroit elected to sign Butler to a future/reserve deal back in January, but he was unfortunately among their final roster cuts at the start of the season.
In 2014, Butler appeared in 11 games and recorded 14 tackles and a pass defense.