Eating the rest of this year makes sense... wouldn't be thrilled about the idea of eating next season because it would reduce your flexibility to do stuff & you're already paying a closer to not play for you, plus paying tax on that since they should be well over next year.What would Jansen and $20 million be worth in prospects? We aren't trading him at full value, especially when we're already below the salary cap.
If you want to up your prospect haul, pay his salary this year & kick in something else the acquiring team may need that doesn't involve limiting yourself next season (prospects you're down on and need to be protected, expiring deals like Hernandez/Duvall which you could also pay for, whatever).