Bigby went undrafted and was signed by the Miami Dolphins in 2005. Miami waived him before the preseason even started, and was picked up a week later by the Jets. New York waived him during final cuts before the 2005 season. Green Bay signed him to their practice squad the following November and he spent the next year-and-a-half on their practice squad. He got some significant playing time with Green Bay, and was even named the NFC Defensive Player of the Month for December 2007.
He would continue to have success playing for the Packers until the Seahawks signed him as a Free Agent last year. He played in 15 games for the Seahawks and became a free agent again at the end of this season.
In a two-year deal worth $2.5 million, with the potential to make $4.5 million, the Chargers have picked up a Strong Safety that will compete with Darrel Stuckey for playing time in Strong Safety and Special Teams. This does not preclude them from targeting another Safety in the draft, but this does help to address a position of need before the draft.
Much like Bob Sanders, Bigby is a hard-hitting Safety. As such, he has had some injury issues in the past and has some trouble consistently staying on the field. His pass coverage leaves some to be desired, so when and if he does play, expect to see him on the field with newly-acquired LB Jarret Johnson on obvious running downs.