Johnson spent the last four years in New York with the Giants. They picked him in the seventh round of the 2007 NFL Draft, and Johnson appeared in every game that season en route to the Giants winning the Super Bowl. A year later he became a starter for the Giants and was in the starting lineup for all 16 regular season games. He started in 14 games in 2009, but last year he only appeared in two games all season.
Johnson had a connection to the Lions even before signing today. His brother is former Lions linebacker, who had his career ended in 1997 when he suffered a spinal cord contusion and had to have his life saved by CPR.
As for Davie, he was one of the first undrafted free agents the Lions worked out a deal with after the lockout. The linebacker from Northwestern seemed to have a legitimate chance to make the team, but that was before the Lions upgraded their linebacker corps during NFL free agency. After that happened his chances greatly diminished, and now he is once again a free agent.