Operating under the assumption that Kevin Towers is not an idiot, why would he entertain the possibility of trading Justin Upton? In assuming Towers isn't an idiot, we're also assuming he knows that Justin Upton is, like, really good at baseball and under team control for the next five years (his age 23-27 seasons) for a reasonable price ($49.5 million).
He's the type of player any team--rebuilding, in contention, collapsing, et cetera--would love to have. So why would Towers consider parting with him?
While Upton is unlikely to regularly repeat his 2009 season into his mid-20's and his 2010 season was viewed by some as a disappointment (111 OPS+ with plus defense in right, the horror), he's still an extremely valuable commodity. ZiPS and PECOTA both agree he'll settle in as a ~.275/.370/.510 hitter through the life of his current contract, which combined with above-average defense makes him worth somewhere between 4.0 and 4.5 wins each year through his age 27 season. If we can reasonably expect Upton to provide around 21.5 wins over the next 5 years and he's owed only $49.5 million for his 2011-2015 services, there's a lot of surplus value associated with his contract; about $45 million worth.
When we're talking about a potential Justin Upton trade, it's important to understand this: Kevin Towers will not be dealing him for crap. Every year of Upton's contract the least-error projection suggests he'll be worth around 4.3 wins, while the team only has to pay him as if he were worth around 2.3 wins. The Diamondbacks would be shipping away 10 free wins if they were to deal Upton, and they'd need to receive at least 10 free wins in return.
Looking at the work that's been done by other BtB'ers on prospect surplus value, a team looking to acquire Upton would need to surrender something like a top-100 hitter and pitcher, a useful MLB reliever with upside, a grade B pitching prospect, and a lottery ticket or two. This is the type of package that would instantly make most of the best of farm systems in the game mediocre.
And that is why Kevin Towers will entertain the idea of trading Justin Upton. He knows Upton is really good, he also knows other teams are willing to give up really good prospects to get him. Don't think of it as Kevin Towers saying, "Does anyone want this guy?", think of it as Kevin Towers saying, "I know you want this guy, the question is how much are you willing to pay to get him?". That's basically what's going on. Towers holds all the cards, here. If an offer blows him away, he'll accept. If not, there's absolutely no pressure for him to move Justin Upton, because he's Justin Upton. It's quite shocking, to me at least, that more teams don't capitalize on the type of situation Towers is currently in by putting young stars on the market before they get too expensive. Championship teams are built in different ways, and I see no reason why with a good scouting department one can't build one by trading away, rather than building around, a young star.
Credit Towers for being creative and putting Upton on the market, and if I were a Diamondbacks fan I wouldn't be adverse to either the team's new leadership in general or the proposition of trading away Justin Upton.