Johnson's salary was reduced last Friday from $6.75 million in 2013 to $715,000 for the rest of the season by converting the rest of his base salary into a pro-rated bonus.
The move opened up $4.26 million in cap space for this year.
Dave Gettleman has taken the Panthers from more than $16 million over the salary cap to now more than $17 million under it since taking over as general manager in January.
The Panthers have discussed with representatives of defensive end Greg Hardy the possibility of extending his deal before he becomes a free agent after this season. They also will need cap space if they plan to move forward with a new deal for quarterback Cam Newton after this season.
Both of those situations could be impacted by the 0-2 start that has the future of coach Ron Rivera in question.