Collins, 25, is a former second-round pick of the Falcons back in 2015. He was in the third year of his four-year, $5.428 million contract when the Falcons elected to cut him loose last season.
Collins signed on with the Colts’ practice squad last month after officially being reinstated by the NFL. Indianapolis promoted him to their active roster last week.
In 2016, Collins appeared in eight games and recorded 31 tackles, two interceptions and 10 pass defenses for the Falcons.
Grissom, 26, is a former third-round pick of the Patriots back in 2015. He spent a portion of his rookie season on the Patriots’ practice squad before being called up in October.
Since then, Grissom has been on and off the Patriots’ active roster.
In 2018, Grissom has appeared in four games for the Patriots and recorded one tackle and no sacks.