For the reasons I'd be weary of trading for Marte, I'm also weary of re-signing Bregman.
With very very few caveats, every player who plays the game completley falls off a cliff and becomes a negative WAR player at some point between 30-35.
We constantly fall into the same trap of assuming a guy, no matter how good is going to continue to do what he's done the last few years over the next few years. When time and time and time again history proves us wrong.
The problem is, we remember the guys who play until 40 like David Ortiz, and we never remember the names of the Matt Kemps of the world. I haven't even thought about Matt Kemp in over a decade but I remember a period of time when we just HAD to trade the farm for him because of how good he was.
Marte could age well, or not. Betting on youth like Mayer over Marte isn't going to net positive results all the time but the vast majority of the time they do. Even if Mayer never amasses the career war that Marte does betting on the Mayers of the world 23-38 over the 33-38 Martes more often than not nets positive results.
Teams will make good moves and bad moves, no one can predict the future, but good teams are the aggregate of many good sound decisions. And again, I don't think it's bad trade, it just does not match what this team needs right now and where they are at. Thats the type of move you make when your window is closing and you're getting desperate. Sox should not be trading from a place of desperation ESPECIALLY considering they're 100% unwilling to spend the money on guys.