The Diamondbacks announced tonight that they have optioned struggling right-hander Shelby Miller to Triple-A Reno. Arizona did not announce a corresponding move at this time.

Just four months ago, this would’ve been an unthinkable outcome for Miller, who was coming off his finest season as a Major Leaguer. The 25-year-old posted a 3.02 ERA with 7.5 K/9 against 3.2 BB/9 in 205 innings in his lone season with the Braves after coming to Atlanta in the December 2014 Jason Heyward swap. That performance led the D-backs to part with an king’s ransom — center fielder Ender Inciarte, 2014 first-round pick Aaron Blair and 2015 No. 1 overall pick Dansby Swanson — to acquire Miller in a trade this summer.

However, the 2016 has been a disaster for Miller, whose 7.14 ERA is the third-highest in all of baseball among pitchers with at least 60 innings pitched. He’s missed some time this season with a finger injury but struggled even in his return from the disabled list, posting a 7.23 ERA over his final four starts prior to the All-Star break. Nick Piecoro of the Arizona Republic tweets that Miller said he understands why he’s being sent down and candidly added that he was surprised it hadn’t happened sooner.

Miller’s trade was among the most talked-about swaps in recent history, as many considered the price paid by the D-backs to be exorbitant in nature. However, even the most adamant detractors of the deal have been surprised by the struggles of Miller, which have played a major role in what has been a disappointing season for the Diamondbacks overall. Arizona lost center fielder A.J. Pollock, one of the game’s top all-around players, for much (if not all) of the 2016 season before Opening Day, and it watched $206.5MM starter Zack Greinke falter out of the gates as well. The D-backs have also lost right-hander Rubby De La Rosa to the disabled list for most of the season to date, and the club’s projected No. 3 starter, Patrick Corbin, has had issues of his own. While Corbin’s woes haven’t been as pronounced as those of Miller, he’s currently toting a 4.94 ERA after pitching to a 3.47 mark between his two most recent healthy seasons (2015 and 2013).

The end result for the Diamondbacks has been a 38-52 record and a last-place standing in the NL West that few would have predicted following their flashy offseason. The D-backs have reluctantly begun to operate as sellers, having already traded Brad Ziegler to the Red Sox.