The Carolina Panthers cleared over $4 million in cap space last week by restructuring the contract of defensive end Charles Johnson a source with knowledge of the situation confirmed on Monday.

Johnson had been earning $6.75 million in base salary and had a cap number of $13 million in 2013 the third season of a six-year $76 million contract extension he signed on July 29 2011. Johnson was paid at the $6.75 million rate in Week 1 but will be paid at the league minimum rate ($715000) for the final 16 weeks to bring his total base salary to $1.07 million.

In exchange for lowering his base salary Johnson received a $5.68 million signing bonus which will be prorated over the next four seasons (2013-16). The move lowered Johnson's cap number this season to $8.74 million a cap savings this year of $4.26 million.

The Panthers had plenty of cap space entering last weekend with $8.369 million in space. The Panthers now have $12.6 million of cap space the sixth-most available cap space in the NFL. Teams can "carry over" space from one year to the next and the stockpiled cap space could create space to use on upcoming extensions for Cam Newton who will be eligible to sign an extension after the 2013 season. The Panthers will also be looking to extend the contract of defensive end Greg Hardy who posted 11 sacks last season.