Nick Piecoro appears to have had the first handle on this:
With Steve Gilbert obtaining confirmation subsequently from that old favorite, "a baseball source." Details are expected to be announced on Friday, but it's a sad end to one of Kevin Towers' less-successful free-agent signings. The 2012 season wasn't actually too bad, with a couple of solid months powering Kubel to a 120 OPS+, and his arm in the outfield helped negate his glacial range. But the 2013 campaign was almost a complete disaster. In fact, here are the ten worst seasons in Diamondbacks' history, as measured by fWAR:
Yep. Kubel's 2013 campaign puts him #1, all-time. Remember how bad Eric Byrnes was in 2008? Kubel was more than half a win worse. That more than wiped out his positive value from last season, and meant that we paid $15 million (less whatever we're getting back from Cleveland, which will likely be very token) for two years of replacement-level play. His power, which was the main redeeming factor of his performance last year, basically evaporated, with only five home-runs, compared to 30 in 2012, and injury didn't help matters either. The writing was pretty much on the wall by the trade deadline, and Kubel had made only two starts since August 3.
He was eventually DFA'd to make room for David Holmberg's spot start, and frankly, I'm astonished that any team saw fit to offer anything in exchange for Kubel. Obviously, a return to the American League is best, where he can DH without having to worry about fielding. But he was just so wretched with the bat of late - since June 22, his line was .141/.211/.192, for a .403 OPS - that it's hard to see why any team would want him. There's a moral to the story here: something about overpaying for fragile veteran outfielders, I think.... [H/T to azshadowwalker for her Fanpost]