Some may not be aware of it. If you restructure a contract and then edit that player later in any way, the cap space you saved with the restructure disappears.
Example:
I restructured my QB’s contract creating a +$13M for the next year from a -$33M.
I edited something on my QB and noticed my Cap space went back to -$33M on the resign players page. I had to edit the contract length of my QB, save the edit, then go back and edit the contract length back to the original length.
After that I was able to restructure the contract again and the cap space went back to +$13M.