Long played just 11 snaps over four games with the Atlanta Falcons in 2015 after suffering ACL tears to his right knee in back-to-back seasons.
Long passed an exit physical with the Falcons in January and another conducted by Dr. James Andrews this week, per Schefter.
Last month, the 31-year-old tackle insisted he was "finally healthy."
"This is the healthiest and best I've felt in probably about five, six years," Long said. "My knee's back. I've just been working out, feeling good and ready for the opportunity when it comes along."
By not agreeing to sign a waiver, that opportunity will not be in Baltimore.