He's cheap enough to keep, you'd probably end up giving some other guy $2 million otherwise, but it depends on the overall picture and bullpen budget.
Phelps gets a big raise if you take his option, Hector gets a raise either way, Morgan gets a raise and Alvarez, being a total free agent, might not be affordable. But I think I'd rather risk $4.5 on Phelps and a rookie than $2.5 million on Hembree and $2 million for another journeyman/fungible.