I don’t have much confidence Johnson is with the Sox in 2019.
He’s cheap and comtrollable, but those seem to be his primary skills. And while being left-handed is sometimes a sought-after commodity, he’s on the one team that doesn’t need LHSP. His value in the bullpen is also mitigated because he isn’t a prototypical side-arming LOOGY who specializes is getting out left-handed hitters and the league-wide strategy of deploying the shift has mitigated the need for that type of specialist.
His roster spot is probably more needed to replace some of the 125 IP the Sox have lost from the bullpen. And while the Sox need starter depth (like every team), they need it to come from AAA where it doesn’t create other voids.
Johnson does have some trade value, largely due to his low salary and MLB experience. A team like Seattle that’s shedding payroll might be willing to take him on as part of a trade.
I could see the Sox dealing Johnson and either Chavis or Dalbec for Colome to help fill the void left by Kimbrel and Kelly. LeClerc is Texas is another candidate...