Rules are a little different from Preston's lists. I took the worst single seasons in WAR from a Diamondback, and selected the worst at each position, where a player had more games at that spot than anywhere else, even if this was less than 50% of the overall total. I also didn't enforce any kind of minimum appearance: if you managed to be the worst at your position in only 40 games, more (Dark Side) power to you.
Catcher: Rod Barajas, 2001 (-1.0 bWAR)
This was a surprise. If there was a season I did not expect to find on the list, it was the one where we took the World Series! But Barajas edged himself out for the honor - he was worth -0.8 bWAR in 2003. All told, over his five seasons with Arizona, he was worth two wins below replacement, but that didn't stop him from racking up 14 years in the major leagues, over which time he earned almost $20 million.
First base: Conor Jackson, 2005 (-1.2 bWAR)
I haz a sad... Though this was not the result of CoJack's well-documented battle with valley fever. No, this was actually his rookie season, where the first-round pick made his debut, and promptly batted exactly at the Uecker Line with a 59 OPS+, racking up enough negative WAR over his 40 games. Mark Trumbo breathes a sigh of relief, for his 2014 campaign - where he played more at 1B than LF - was next, at -1.1 bWAR.
Second base: Aaron Hill, 2014 (-1.2 bWAR)
The most recent name to make the list, we are now obligated to talk badly about Hill, since he is no longer with the organization... He also played more often than any of the others, being our everyday 2B and appearing 133 times for Arizona that year. While his hitting was no great shakes (81 OPS+), his negative impact was largely the result of weak defense - while the same dWAR as 2013, the evaporation of his bat exposed that aspect more.
Shortstop: Tony Womack, 2003 (-1.3 bWAR)
Womack, of course, had his moments: stealing an amazing 72 bases for us in 1999, walking us off in the winner take all Game 5 of the 2001 NLDS against the Cardinals. But his skill-set did not age wel, and by 2003, he was a weak slap hitter (53 OPS+) with sharply-declining speed and a questionable glove. Though he did rebound to a solid 2004 - ironically, with those same Cardinals he beat - this year was the beginning of the end for Tony.
Third-base: Tony Abreu, 2010 (-1.3 bWAR)
Abreu was the player named later after Jon Garland was dealt to the Dodgers during a game against them. At the time, Josh Byrnes said Tony had "the ability to play many infield positions and can swing the bat." Well, if technically true; then, I can play many infield positions and swing the bat. Play well and make contact? Not so much. Abreu's OPS+ was 47 and he made 10 infield errors while starting only 39 games.
Left-field: Eric Byrnes, 2008 (-1.4 bWAR)
Way to repay that contract extension, Eric. His dodgy hamstring limited him to just 52 games, but it was enough to pile up more negative bWAR than any other LF, including Trumbo and Jason Kubel. I'm not sure what was more painful for D-backs fans. Knowing Byrnes was paid $6.7 million for his wretched performance, or enduring re-runs of Eric Byrnes Show episodes during rain delays. I still can't hear "Josie's on a vacation far away" without cringing.
Center-field: Jose Cruz, 2005 (-1.3 bWAR)
This was another surprise, mostly because I had completed forgotten Cruz was a Diamondback. We've had some great CF over the years: Steve Finley, Chris Young and now A.J. Pollock. But Cruz was not one. Again, he managed this in less than half a season, being dealt to Boston at the trade deadline that year. Ironically, he was acquired by Arizona for Casey Fossum - who also appears in this article, a little further down.
Right-field: Brent Brede, 1998 (-1.9 bWAR)
Clearly the toughest spot: four of the five worst seasons all-time by D-backs came from players who were primarily here. Brede narrowly beat out Quinton McCracken (-1.7, 2003), Karim Garcia (-1.5, also 1998) and Yasmany Tomas (-1.3, this year) for the honor. Brede couldn't hit (68 OPS), couldn't field (-1.5 dWAR) and didn't play in the majors again. Fun fact: caught the final out in the game where Barry Bonds was intentionally walked with the bases loaded.
Omar Daal, 2000 (-2.0 bWAR)
Russ Ortiz, 2005 (-1.7 bWAR)
Ian Kennedy, 2013 (-1.5 bWAR)
Edgar Gonzalez, 2004 (-1.5 bWAR)
Casey Fossum, 2004 (-1.4 bWAR)
I think I just threw up in my mouth a little. I was, however, impressed to find someone actually worse than the Huge Manatee, Russ Ortiz. But then, Daal was awful in 2000: the Diamondbacks were 4-16 in games where he took the mound. And that "4" was largely because of the offense, which scored a total of 36 runs in those four contests - Daal still only won two of them. He went 2-10 with a 7.22 ERA, and was traded to the Phillies, where he continued to suck. Omar had chances to become the only National Leaguer since Phil Niekro in 1979 to lose 20 in a year, but the Phillies won his last two outings, scoring six and 10 runs for him.
Kennedy's presence is also unexpected, though represents perhaps the sharpest fall from grace, having gone 36-16 with a 117 ERA+ over the previous two seasons with Arizona. He really hasn't been the same since, with an ERA+ of 88 from 2013-15, though that didn't stop him from being signed to a $70 million contract by the Royals this winter. Gonzalez and Fossum round out the Worst Ever Rotation, both stemming from the horror which was 2004. No less than thirteen separate Diamondbacks pitchers that year were worth -0.3 bWAR or lower. Without the Big Unit and his 8.5 bWAR, the entire staff would collectively have been 2.6 wins below replacement.
Chad Qualls, 2010 (-2.2 bWAR)
Trevor Cahill, 2014 (-1.5 bWAR)
Brian Bruney, 2005 (-1.5 bWAR)
Eddie Oropesa, 2002 (-1.4 bWAR)
Clint Sodowsky, 1998 (-1.2 bWAR)
Aaron Heilman, 2011 (-1.1 bWAR)
Brandon Lyon, 2005 (-1.1 bWAR)
A "well done" to Qualls, for being the worst pitcher, by bWAR, in Diamondbacks' history, even though he only pitched 38 innings for us that season. They were, however, spectacularly bad: an ERA of 8.29 despite Qualls having picked up 24 saves the preceding year. Next is Cahill, who wasn't really a starter or a reliever (17 starts, 15 relief appearances), but I slotted him in here to maximize the overall suck. The rest of the names are largely ones which history has buried, save for Oropesa (possessor of quite a back-story), who will be a coach in our farm system, with Double-A Mobile this season.