Lewis, 28, is a former seventh-round pick of the Lions back in 2012. Lewis played out his rookie contract with Detroit before signing a one-year, $810,000 contract with the Vikings back in March.
In 2015, Lewis appeared in 15 games for the Lions and recorded 21 tackles and a sack.
Gaston, 24, originally signed on with the Cardinals as an undrafted free agent out of Purdue back in May of 2014. Since then, he’s had brief stints with the Patriots and Dolphins before the Packers signed him to their active roster towards the end of the 2014 season.
Green Bay wound up waiving Gaston during the season before later adding him to their practice squad. Gaston later caught on with the Bears last October, but they elected to cut him loose in May.
The Vikings just signed Gaston to a contract a few weeks ago.
In 2015, Gaston appeared in nine games and recorded 12 tackles and a sack.