Here is the team's announcement:
Rosenthal, 27, blew out his elbow and underwent Tommy John surgery in August. He is expected to miss most, if not all, of the 2018 season. Before the injury this year he saved 11 games with a 3.40 ERA and 76 strikeouts in 46 2/3 innings. He has a career 2.99 ERA and 121 saves in parts of six big league seasons.
The Cardinals released Rosenthal not necessarily because they want to move on from him entirely. In fact, the team figures to try to re-sign him to a new contract. Rosenthal was originally scheduled to become a free agent after next season. His 2018 salary through arbitration was going to be substantial -- MLB Trade Rumors projected $7.9 million -- so, rather than pay that big salary while Rosenthal rehabs from Tommy John surgery, the team cut him loose.
MLB's rules stipulate you can not cut a player's salary to less than 80 percent of his previous year's salary. Rosenthal earned $6.4 million in 2017, so the Cardinals would've had to pay him no less than $5.12 million in 2018. That's still an awful lot of money for an injured pitcher. And injured pitcher who will become a free agent after the season, no less. You could pay him all that money to rehab only to watch him walk as a free agent.
By releasing Rosenthal now, the Cardinals get a clean slate financially. They can re-sign him to a contract of any size and any length, let him rehab in 2018, and see where it goes after that. The going rate for a pitcher rehabbing from Tommy John surgery these days is a one-year deal worth $2 million or so, with a club option for a second year. That way when the player gets healthy, the team can bring him back.
Of course, other clubs can now make Rosenthal a similar offer. The Cardinals are taking a bit of a gamble here that Rosenthal will return to them, the only team he's ever known, rather then spend next year rehabbing with a new organization. Point is, Monday's release does not end Rosenthal's time with St. Louis. They now figure to try to re-sign him to a smaller contract that keeps him with the team beyond 2018.