Casas has some trade value, but I am not so sure he represents the key chip in a trade for a frontline starting pitcher. He won’t get you Crochet, for example. Probably someone more along the lines of Casey Mize. (Probably not available. See SF below.)
With their new, expensive SS, pre-arb Casas would be a big plus in SF. But a team spending on moving forward into the postseason isn’t giving up SP.
And Bregman has had a really good career, but he also turns 31 right around opening day. He’s entering the Waning Years, and he’s not likely to take a deal of 3 years or less. How much should the Sox pay him as he slowly devolves into Overpriced Obsolescence?