P91 is making some hyperbolic statements here but I do agree we need at least one more arm.
I’m also not very concerned about it. Just think about the 15 or so bullpens making additions (NYY, TB, OAK, HOU, CLE, LAD, ATL, PHI, NYM, STL, MIL, COL, CHC, LAA, WAS, CWS, SD). Most of those are already full. Kimbrel and Ottavino have a choice between being a closer in Boston or Atlanta or a 7th inning guy elsewhere. Except for the Rays, there are really no other 8th inning jobs on possible contenders available, let alone 9th inning jobs.
If both of them sign elsewhere, I think one of Madson, Brach, Sipp, Kelley, or Perez signs with the Sox at <$5M/yr (maybe a two-year deal at that amount), and it’s fine. And I think there’s a good shot that Brewer, Putnam, or Smith — maybe two of them — puts up a 3.50 FIP over 50-60 innings. If it comes to it, DD should also be able to trade for an arb guy like Smith, Watson, Bradley, Chafin, Rogers, Hardy, or Greene pretty easily by taking on salary.