Johnson, a third-year veteran who entered the NFL as an undrafted free agent, has been with the Tampa Bay Buccaneers (2010-12) and Minnesota Vikings (2012-13). He has played in 11 career games and was released by the Vikings last week.
At 6-foot-4 and 270 pounds, he projects as a defensive end in the team's system, where the Patriots have starters Chandler Jones and Rob Ninkovich atop the depth chart, with rookie Michael Buchanan and second-year player Jake Bequette the backups.
Kearse, at 6-5 and 310 pounds, projects to defensive tackle in the Patriots system. He spent the last two-plus seasons with the Carolina Panthers, appearing in 14 games (8 starts), and was waived/injured by the club at the end of the 2013 preseason (knee).
The Patriots are thin at defensive tackle, having lost Vince Wilfork to a season-ending Achilles injury and with veteran Tommy Kelly (right knee) missing Sunday's win over the Saints. Rookies Joe Vellano and Chris Jones, along with first-year player Marcus Forston, are the next players on the depth chart.
The team signed veteran four-year veteran Andre Neblett last Wednesday, but he was waived on Saturday in favor of Forston. Neblett cleared waivers today and is free to sign with any team.