White, 30, was primarily a special-teams presence last year for New England, registering 18 tackles on special teams - good for second place on the team. McGowan missed the 2010 season with a chest injury but the veteran recorded 79 tackles in 2009, when he started 11 games.
Neither player will be able to practice until August 4th or the start of the NFL League Year, whichever comes first. The league year will start once the NFLPA re-certifies and votes to approve the new collective bargaining agreement.
The team also announced that undrafted free agent Anthony Leonard has been waived for the purpose of being placed on injured reserve, although ESPNBoston.com reports that it didn't appear as though Leonard suffered any injury during his participation in a full morning session on Saturday.