Free agency begins March 13.
General manager A.J. Smith says the team would like to keep Jackson "but other teams now will enter the picture."
The Chargers also released defensive end Luis Castillo, a 2005 first-round pick who started 79 games. He had 19 sacks and 43 tackles for loss.
Castillo injured his tibia in the 2011 opener and missed the rest of the season.