Pleasant appeared in all 16 games with the Houston Texans in 2017, notching 27 total tackles, two sacks, one interception, one forced fumble and five special teams tackles.
In his six NFL seasons with Houston, the 29-year-old Pleasant appeared in 78 games, making one start. He has three interceptions, 2.5 sacks and 17 passes defensed.
Theaker, 24, spent last season on the practice squads of the Dallas Cowboys and New Orleans Saints. Released by the Saints in May, he appeared in 42 games at Wayne State, making 33 starts at right guard and both tackle positions.
In another move, New England released wide receiver Cody Hollister, who spent the entire 2017 campaign on the team’s practice squad.