Before the first game of the season in 2013, Tom Telesco was able to restructure Philip Rivers' contract to free up $1.67M in cap space. At that time, the Chargers were dangerously tight on cap space. While not as tight this year, history has repeated itself as Antonio Gates took a restructure today that reduces his base salary, but gives him an equivalent amount of bonus.
Sources report that Gates has reduced his salary from $5M to $2M in exchange for a $3M restructure bonus. This is a move to transfer some cap burden to a later year as the $3M bonus can be split between this year and next year's cap. This provides the team with $1.5M in additional space this year.
For those of you with an eye the team's free cap space, my calculations have us at a shade under $4M. In order to provide updates more frequently, I will be maintaining my spreadsheet here. Bookmark if you want to stay updated.
Update: I uploaded an old spreadsheet. It has since been fixed.