The Titans seemingly mulled keeping Marc Mariani on the active roster or placing him on the PUP list, but at the end of the day they knew this wasn't his year.
Titans fans have been pulling for the Montana all-star since he was a late round selection from the Fisher era. Mariani's career was highlighted by a Pro Bowl season two years ago, but since then he has been plagued by injuries.
This move actually may have been the best move for #83 considering the alternative. Darius Reynaud has proven time and time again that he is the right KR/PR for this team, so it is hard to imagine that Mariani would make the team there. As a WR, Mariani would need to find a way to beat out Britt, Washington, Wright, Hunter, Williams, or Preston if he was hoping to see playing time there.
With uphill odds like that Mariani may be better to focus on developing his skills as a WR in hopes of taking advantage of a situation next year where Britt, Williams, and Washington are all free agents.