Re: NT Concern...
Mario was definitely a cap casualty.
There was no way that the Texans can retain him, unless they restructured a whole bunch of contracts and push the deficit onto later years.
Or they would have to cut other guys with high cap space (Antonio for example).
Dreessen's new contract with the Broncos only took up $1.833M in cap space last year, so they could have resigned him if they wanted to (along the way, they probably cut a receiver who earned little just to make room on the roster, or any player really, from Barrett Rudd to Alan Ball to Shilo Keo - they may make little like in the $400-600K range; minimum guys.)
They would still be about a Mil under the cap.
If they feel comfortable without Dreessen, they can opt not to resign him so that they have the room to sign another player. In this case, it would be a cap relief.
You release some money at one position in order to sign another player at a different position.