According to people involved in the trade, the deal sending Justin Upton from Arizona to the Braves is done, complete, and an announcement is expected to be made later today.
So, why didn't Upton end up on the Mets?
People aware of the situation say Arizona talked with the Mets early in off season, and again at various points during the last two weeks. The Mets were always interested in Upton (not Jason Kubel). However, from the start, the D-Backs were looking to acquire a big-league infielder, as well as a collection of pitching prospects, which is why they rejected Rangers 3B Mike Olt and spent much of the winter trying to wrangle a third team to pry away a player like Braves SS Andrelton Simmons. The Mets never had the necessary, impact infielder, and they made it clear early they would not be trading Zack Wheeler and Matt Harvey.
In the end, knowing Arizona's interests, I assume the Mets best offer could have been something like Daniel Murphy or Ruben Tejada, 3B prospect Wilmer Flores, a Josh Edgin and one or two less-established pitching prospects. But, it seems talks never even got that far.
The Braves deal would always have been significantly better with Martin Prado involved.
As a result, the Rangers and Mets had only sporadic, and short-lived conversations with Arizona during couple of weeks, and it sounds like the Braves were essentially the only legit option after Upton rejected a deal with the Mariners.