If the Sox can reset and spend a little, they could fill some gaps through free agency. Some names that appeal to me
SP: Trevor Bauer is the obvious target. He'll cost and have some sort of evil long term contract, but the Sox need arms. Fallback options include Marcus Stroman and Robbie Ray. Beyond that, some depth signings with some intrigue include Mike Minor and Jake Odirizzi. Outside of Bauer, none of these are real game changers. Garrett Richards is a mega talent who would probably be better off moving to closer.
RP. Weak year for RP, but Kirby Yates, Ken Giles, Keone Kela, Trevor May and Liam Hendriks. Chris Devenski is a reasonably good non-closer who is available.
2B: Assuming the Sox do not try to solve this in-house from the Utility Infielder Crowd, Cesar Hernandez is a very underrated player. Jonathan Schoop will be available again this year, like he is every year, and is apparently a very good friend of Xander Bogaerts. Jonathan Villar has become a useful player as well, which no one saw coming.
CF: Springer is the headliner and only real game changer, but maybe that money is better spent on pitching. Beyond him, the best options are the players Boston is losing, in Bradley and Pillar. Sox are probably better off avoiding Springer, as he is likely to be one of the two biggest draws in this class (along with Bauer).
OF: Now the Sox could move on a corner OF and switch Benintendi to CF, which is not anyone's wish on this forum. But if that happens, Marcell Ozuna and Nick Castellanos (if he opts out) become the bigger names. Joc Pederson would also be available, but unless someone gives him a chance to learn to hit LHP, the interest should be limited. I suppose either Ozuna or Pederson are as capable in CF as Benintendi...