There's absolutely no need to trade Mayer. They can accomplish what they need to without doing that, so it would be just plain stupid and shortsighted. Ain't happening.
That's one of the issues, his value is a little depressed right now.
He's still a top prospect, though. Why trade him when you can buy starting pitching? Starting pitching is the one thing in relative abundance in this free agent market.
DD actually lived with Farrell for 2 years.
Trading for Kimbrel was virtually the first thing DD did, as notin will attest.
He traded for Sale after his first year.
He had a 3.1 bWAR, 2.5 fWAR, so he earned his contract. Nobody that's followed his career would have projected him for more than 150-160 innings, so the 144 wasn't disastrously low.
He would have been #2 in innings on the Red Sox.
I think his public skills would have seemed much better if the team won more games, though, and no amount of skills was going to compensate for back to back 78-84 seasons.