Mager, 25, is a former third-round pick by the Chargers in the 2015 NFL Draft. He is in the second year of a four-year, $2.994 million rookie contract that included a $680,120 signing bonus and made a base salary of $615,000 this season.
He missed time last season due to a shoulder injury and a concussion.
In 2016, Mager appeared in 11 games for the Chargers and recorded 31 total tackles, one interceptions, one fumble recovery and four pass defenses. He also accumulated 63 kickoff return yards. ProFootballFocus rated him as the No. 114 overall cornerback out of 119 qualifying players.