I don't think KCamp would be a good 3B, but that's not really based on anything.
The Devers is a bad 3B & Bregman is a good 3B stuff is interesting. & while it's true... it's interesting trying to figure out how much it actually matters.
I like OAA better than DRS, so we'll use FRV for this, which is basically the translation of outs to runs.
Devers was a -5 last year & Bregman was +5 runs. So, if that's accurate, over the course of the season, having Bregman at 3B instead of Devers would have allowed the Red Sox to prevent 10 runs on the season.
The Red Sox allowed 747 runs last year, so with Bregman they allow 737. They scored 751 runs.
That would increase their pythag wins from 81.5 to 82.5. So that's not nothing, but it's also not like a big needle mover. Bregman is also 2.5 years older than Devers so one would generally expect his defense to fall off sooner, but there are of course arguments to the contrary.
The other piece is the offense. If we sign Bregman with the intention of replacing Yoshida by moving Devers to DH, the other piece is how many runs more do you score with Bregman over Yoshida?
Bregman had a .323 xwOBA & a 118 wRC+ last year, & Steamer projects him for 122 next year.
Yoshida, who is about 9 months older than Bregman, had a .324 xwOBA & a 115 wRC+, & Steamer projects him for a 117 next year.
Steamer projects Bregman to be worth 15.3 runs above average offensively in 664 PAs & Yoshida to be worth 8.4 in 520. While it is reasonable to project that Bregman may have more PAs in a full season than Yoshida, that's not particularly descriptive if Yoshida is complemented by a Refsnyder or someone. But rather than getting too into the weeds on that, let's just give Yoshida the same # of PAs as Bregman which would take him to 10.7 RAA.
So in the same # of PAs, Steamer projects Bregman to be worth 4.6 more runs. Let's round that to 5.
So in Bregman world, the Red Sox have now outscored their opponents 756 to 737, which is a pythag of 83.1.
So using this really rough mathmatical construct, Bregman at 3B & Devers at DH is worth about 1.6 wins more than Devers at 3B & Yoshida at DH.
Is a marginal increase of 1.6 wins worth $30m per year, their 2nd round pick & $500k of IFA $? I guess it's hard to say in a vacuum. Technically they could probably be able to save about $7m/year of that amount by subsidizing Yoshida.
I just realized if I use Steamer projections they only predict a 5.6 run difference on defense between Bregman & Devers for '25, so using that we are back to about 1 marginal win by adding Bregman, but either way.
Let's compare that to the catcher situation, though...Steamer projects Wong will be worth -4.4 runs on offense & -3.0 runs on defense in 369 PAs & Narváez for -4.2 & 3.7 in 194 PAs...
The oddest thing is if that's accurate, they could improve by 3 runs just by switching Narváez to Wong's PAs & Wong to Narváez's.
But for the sake of this exercise, let's just plan on replacing Wong & letting Narváez be the backup.
Yasmani Grandal has a Steamer projection of -1.8 offense & 5.3 defense in 240 PAs. If you give him Wong's 369 PAs, that would be a total of +5.4 runs, compared to Wong's -7.4 runs. That's a swing of 12.8 runs...rounding we will call it scoring 2 more runs & allowing 11 less.
So in Grandal over Wong world we're at 753 to 736, for a pythag of 82.8 wins.
So Bregman is worth 1.6 marginal wins & Grandal is worth 1.3 marginal wins.
Grandal is a free agent who signed a 1 year, $2.5m contract last off season. He would not require a long term commitment, or cause the Red Sox to lose a draft pick or IFA money.
I mean, of course they can do more than one thing... but I think the main thing this exercise illustrates is how much easier it is of a fit to upgrade at catcher than it is by adding Bregman.
Another guy who has been thrown out there is Sean Murphy, who Steamer projects at +1.5 & +10.6 in 420 PAs. If we give him all of Wong's PAs, & 51 of Narváez's it's a 19.7 run swing (83.8 pythag).
Murphy would obviously require some sort of trade compensation, but he has 4/$60m renaining on his contract with a team option for '29, & his AAV is only $12.2m. Not sure if that bumps up to $15m if he's traded. They keep changing the rules on that stuff, but either way.