I don't think there are three players left out there that are going to bridge the 12-15 win gap for real contention. Soto is one of the few guys like Mookie, Ohtani, Judge, and Witt that could do that. A top SP can make about 2 - 2.5 wins of difference at best from Pivetta, Criswell and Bello who while weren't great, were not awful.I'm going to defend TomRicardo a bit and reiterate that I think Devers is overrated. He is indeed a very good, but not great player. His splits don't do him any favors, same with his capacity to stay healthy, and his fielding. And I agree that's he's not likely to improve on any of those fronts. Trading him would be a Brad Stevens kind of move, akin to trading Marcus Smart. Though part II of a Smart type trade would be to improve the team here and now. That's where I disagree with Tom: I think the team is just about 3 acquired players (plus the rising youngsters) from being a contender.
You are going to close that gap at this point with Anthony and Mayer becoming 3.5-4+ WAR players and improving 2B. Casas is more likely to be more valuable than Devers if not still in his ballpark next year. I just think that is going to take a year or two at this point. That said they need to clear up the trainwreck of roster they have right now to give the younger players reps and build into something. There just isn't a continued value to have Trevor Story and Yoshida here anymore.
I am not saying the Red Sox shouldn't go attack the pitching market, however they should not dump Casas to make room for Devers who probably isn't that much better (don't think a guy who has put so little into his improvement over the last six years is going to pick up a new position lickety split)
Devers is a bit overrated on this board. He is a good 3B but he is not a hall of fame talent. He is a consistent 3.5-4.0 WAR player even if he had a shoulder issue last year. There is value there with this, most likely being at its zenith right now. While I would bet that Casas has a better season than him next year, I wouldn't bet a lot. Devers is very consistent and why he would have value to Seattle who are being offered a fairly inferior Bohm right now. I am not saying dump him like I would with Story and Yoshida. But I think you could get a ton a value offering him to a Seattle right now, more so than Casas even if I value Casas more right now because of where the Red Sox are. Seattle is just in a better place this year than the Red Sox are though the Red Sox will most likely be better in 2 years.
People need to be realistic about where this team and the options left on the table. Chapman was a poor signing unless they really felt they had Soto but it was a low risk bad move.