When Doug Free is removed from the active roster, he'll likely be place on Reserve/Retired, his $5M base salary comes off the books with a minimum salary ($540K) taking his spot in the top 51.
The net salary cap savings is $4.46M.
There would still be $2.5M in dead money from a past signing bonus counting against the cap this year and the Cowboys could ask for Free to re-pay it, but I doubt they will.
Rumors of Free's impending retirement surfaced at the scouting combine last week, so I doubt the team was blindsided by the news today.
Chaz Green has plenty of talent to handle the job and he now knows RT is his to lose, but another legit option needs to be found.
Bring on the competition.