I'm hesitant to say anything, because the last time I wrote a piece speculating on the team's choices in a particular area, they rendered it largely moot a few minutes later, by exercising J.J. Putz's contract. Still, there are plenty of indications the team is not done with their off-season work. Here are some section in which the team especially might be looking to make moves, with the window to sign free agents opening on Thursday evening.
Further thinning of the outfield herd.
There may be some fairly strong differences on who you think might be moved, but whether you're Ken Rosenthal or Nick Piecoro, the general consensus is that the Diamondbacks will probably be looking to trade another outfielder from our depth, with the likely aim of filling one of the sections we'll get to in a little while. At the present time, it appears that Adam Eaton is the only player who is guaranteed to have a job for next season, with Justin Upton, Jason Kubel and Gerardo Parra all having pluses and minuses to their being shifted, in terms of issues such as money saved, likely return, and impact on the 2013 line-up.
I think it's a topic which probably deserves fuller consideration in a piece of its own - as noted above, expect that to appear immediately before the trade is officially announced!
Veteran starting pitcher
At the present time, the 2013 starting rotation would be something like Ian Kennedy, Wade Miley, Trevor Cahill and two from Trevor Bauer, Tyler Skaggs and Patrick Corbin. Kennedy, at age 28, will be the oldest of the bunch by more than three years, and as we've seen, Towers also appears to be a fan of starting pitching depth. I'm with him there - last year, Arizona used nine different starters, which is actually one below the major-league median. [The Padres led the way with 15, a number not surpassed in the National League since the Reds tried 17 different starters in the 2003 campaign]
Looking at the list of free-agents, there are some interesting names there - though, of course, the ones I'd most like to see in a Diamondbacks uniform (hello, Zack Greinke!) are the ones least likely to be acquired, due to the resulting competition. I note the presence of a number of former Arizona players, in the form of Dan Haren, Edwin Jackson and Joe Saunders. You could also include Jason Marquis on the list, someone already acquired once by Towers (though if you blinked, you probably missed his starts for us), and who pitched reasonably effectively in the second half for San Diego, putting up an ERA of 4.04 for them.
Of course, free agency is but one tool in Towers' bag, and a trade is perhaps a more likely route.
There's a mutual option for Henry Blanco at $1.24 million. There's no doubt Blanco has had a positive impact on Miguel Montero, but now that Miggy has signed his big boy's contract, one suspects the need for a mentor is likely less. Blanco is now 41, and injury helped limit him to only 21 appearances last season. Though he wasn't exactly playing regularly, even when fully fit, e.g. he started only three of our 27 games in July. That's probably a good thing, since no catcher Blanco's age has appeared in even 40 games for his team, since Carlton Fisk in 1992. This is partly because only four have even played: Brad Ausmus, Pat Borders, Fisk and Sandy Alomar. It's the knees.
Another possibility is Wil Nieves, who is under team control, though sources differ as to whether he'd be second- or third-year (B-R.com says the former, MLBTradeRumors.com the latter). Either way, he'd likely not make much more than a million dollars - he earned $775,000 this season, and produced well enough last season, both with us and the Rockies. At 35, his knees are likely a little more reliable than Blanco's, and with all respect to Konrad Schmidt, it's not as if he'd be taking playing time away from a hot prospect.
This was definitely an area of concern for the Diamondbacks: last year, our southpaw relievers had a combined ERA of 4.51. Things were actually a good deal worse than that, because the tally includes solid work out of the bullpen by both Patrick Corbin and Wade Miley (who likely won't be there next year, though shoe floated the suggestion of using Corbin as a reliever), as well as Craig Breslow, who was traded for the Red Sox's Matt Albers, in one of the more baffling deals of the year. Yes, I know we got a lot more control, but it left Arizona using Mike Zagurski as our left-handed specialist, and left-handed batters enjoyed him to the tune of a .298 average. So now we're left needing to fill the hole again.
The question here is, will Chris Johnson prove adequate on a full-time basis? He was solidly productive after arriving from Houston, and certainly didn't rely on any help from Chase Field, where his OPS this year was .530. His OPS+ overall, across his time with both the Astros and Diamondbacks, was 108 over 528 plate-appearances. That's not far off his numbers prior to this year (98), so I'm hoping we're not dealing with a Ryan Roberts-like overperformance (Roberts also had a 108 OPS+ in 2011, but that was after an 88 figure for his previous career). In this area, it perhaps helps that Johnson is younger, only turning 28 on October 1st.
A left-handed backup, ideally one who can play both third and first, would typically be the sort of thing the team might look into - Ryan Wheeler fits the description, though didn't really show the power you'd generally expect from a corner infielder. However, curiously for a right-hander, Johnson continued to struggle against left-handed pitching, showing a reverse split from what you'd expect. His career OPS of .667 is more than 100 points worse against LHP, with a line of .255/.294/.372 [Contrast Paul Goldschmidt, whose OPS is 200+ points better facing southpaws] So, it's not clear whether we should be looking for the obvious platoon partner or not.