Discounting first-base, since Chip Hale might as well go ahead and have 162 line-up cards pre-printed with Paul Goldschmidt's name on them, the team has five players in the forefront for the remaining three spots. There are veterans Aaron Hill and Cliff Pennington, younglings Chris Owings and Didi Gregorius, and finally, Jake Lamb, whose rookie status will be intact in 2015. There is some platoon potential, with Pennington (at least technically) a switch hitter, and Gregorius + Lamb left-handers, but you're still left with the prospect on an every day basis of either having a lot of salary on the bench, or sitting the young players and potentially stunting their development.
Another of those lovely gifts left behind by those who have departed, Hill is under contract for $12 million, both next year and in 2016. Last season, he was comfortably below replacement level (-0.7 fWAR, -1.2 bWAR) and easily the least productive of the five. While not impossible - he is only two years removed from a five WAR season - the odds of getting enough production out of him to justify that salary going forward seem slim. The problem is finding anyone else willing to take him off our hands. At this point, he's basically a sunk cost, and his value can't go any lower, so might as well see if there's a rebound.
Quite a number of people have speculated that Pennington could be a non-tender candidate, with MLB Trade Rumors projecting a final-year arbitration salary of $3.3 million. That's not excessive, considering he has been worth 1.0-1.7 wins each of the past two years, but if the D-backs are intent on getting their salary bill back down to the low 90's, it seems a pointless luxury in a rebuilding year. However, Dave Stewart thinks otherwise, Jack Magruder saying Cliff "will be offered arbitration at the deadline. Stewart considers him a valuable piece moving forward." But does that mean valuable as a trade chip?
Based on 2014 performances, Owings definitely had the better year than Gregorius, which is particularly impressive since he's 18 months younger than Didi. In about half a season's worth of playing time (332 PA), he hit .276 with six home-runs. There weren't that many players his age appearing more regularly in the National League; only Bryce Harper and Christian Yelich has more PAs than Owings, so it seems clear Chris's best years are still almost certainly ahead of him. As the closest we have to a "sure thing" in terms of production among these five, I would be inclined to stick Owings at shortstop everyday, and arrange the rest around him.
After going in to 2014 as the de facto starting shortstop, Gregorius's progress sputtered as he batted only .226 for the season, and saw his OPS drop to .650. While not disastrous for the position, considering the MLB average at shortstop was .678, Didi didn't build on his rookie campaign, and at this point, it seems any long-term future in the desert will more likely be at second, where he started seven games in June and July. LHP continued to destroy Gregorius, though if there's a side to be weak against, that'd be it. Still, even with a small sample-size warning, a line there of .137/.228/.196 isn't going to get you more playing time.
Our top-rated position prospect hit the major leagues in August, and... Well, didn't exactly set them on fire out of the gate, batting .230 with an OPS+ of 75 - note, he's actually ten months older than Owings. Early days though, and the trade of Prado certainly opens things up for Lamb to establish himself as the full-time replacement at third. He'll also need to show he can hit left-handed pitching, but I'm more optimistic the MLB struggles were purely SSS, since he didn't seem to have a particular problem with them in the minors. And if he doesn't... Well, there's always Brandon Drury, waiting in the wings...
Stewart on trading
It doesn't seem our GM necessarily thinks there is an absolute necessity to trade. Said Stewart, "We've got to be really, really careful in the area of subtracting from our depth, because it could eventually hurt our team, especially if a guy goes down and we weaken ourselves." There's certainly sense to that: we saw it last year in the outfield where nobody played 120 games and the starting trio of Mark Trumbo, A.J. Pollock and Cody Ross each ended up missing almost half the year. But when the team has obvious flaws elsewhere, e.g. starting pitching, having good players not playing, who could be traded to help those weak spots, arguably hurts more.
At least you can't say Stewart is repeating the Kevin Towers mistake of cutting the ground out from under the feet of those he's trying to trade. Indeed, he seems to be talking up Gregorius, Owings, etc. "It has to be something that's pretty earth shattering for me to move one of my guys... Any time you've got a surplus of quality middle infielders that obviously gives you an opportunity to maybe improve in areas we need to improve. So a position of power, I wouldn't say that, but it does make it a little bit more attractive to try to get to where we want to be, if that's what we decide that's what we want to do."
Shuffling the positions
Perhaps a clue toward how things are going to work, can be found in Hill making seven starts over the last month of the season at third-base. He didn't disgrace himself there, with zero errors in 15 chances, so it wouldn't surprise me to see more of this in spring training next season. When facing a left-handed starting pitcher, we could see Pennington at second, Owings at short and Hill at third, which could maximize the offense without causing too much impact on defense, presuming Aaron is able to handle the shift to third (and since it's down the defensive spectrum, that should be doable). The platoon advantage may also help inflate Hill's numbers for trade purposes.
With a right-hander on the mound - which would be most of the time - we'll have Gregorius, Owings and Lamb from second through short to third, which would give us a long look at them. [The good thing about having no expectations of contention in 2015 is, it gives a good laboratory to test out young players] It would be achievable from a roster perspective too. Assuming a standard five-man bench, this would include a back-up catcher and fourth outfielder (whoever they might be), a rotating two of these five infielders, and perhaps a left-handed power guy off the bench, who can play first-base and spell Goldschmidt once a month. Are we sure Eric Chavez has retired?
Of course, there are still close to five months between now and Opening Day 2015, and it's likely the situation will change between now and then, for one reason or another. It'll be interesting to see how new guys Stewart and Hale sort things out.