The Diamondbacks are atop the National League West despite being barely over ,500. As such, they were able to claim Adam Dunn off of waivers from the Reds (as any team with a worse record is not contending and therefore has no need for Dunn), The DBacks and Reds worked out a deal, and Dunn is heading west. How much does he improve Arizona?
I don't know whether or not he likes baseball, but I do know that Adam Dunn has consistently posted excellent on-base percentages and slugging percentages, while hitting for a terrible average and striking out a ton. Using Marcel's quick-and-dirty projection, we see that Dunn is projected to hit .237/.383/.513 during the rest of the season, which sounds about right. Using a simple runs created formula, Dunn is worth approximately 94.28 runs over the rest of the season.
The question becomes: who does he replace? Defensively, Dunn is relegated to left field (and he plays it poorly at that). The Diamondbacks currently have Eric Byrnes and Justin Upton on the DL, with Upton slated to return soon and Byrnes done for the year. Meanwhile, Conor Jackson is attempting to hold down the fort in left, while Chad Tracy occupies Jackson's former spot at first (with Mark Reynolds handling the duties at third).
Assuming Justin Upton comes back healthy, the Diamondbacks will likely once again resume playing him every day - even though he's been pretty bad since his hot start, Upton plays excellent defense and still draws enough walks to be useful (plus, the at bats are important in his long-term development). The obvious option is to return Jackson to first base, bench Tracy (and let him spell Reynolds and Jackson as necessary), and hope Dunn doesn't do too much damage in left field.
But Chad Tracy is a solid player. Marcel projects him to hit .280/.344/.464 during the rest of the season, good enough for 81.67 runs created. If the Diamondbacks chose to sit Tracy in favor of Dunn, they'd likely create approximately 10 more runs (after all, Tracy would still be available off the bench), which equates to one win.
Orlando Hudson recently got hurt, taking another solid bat out of a lineup that already struggled to score runs. Hudson is likely done for the season, creating a rather gaping hole at second base - a hole that the Diamondbacks plan to plug with Augie Ojeda. Although he has a great name, Ojeda is projected to hit only .263/.347/.371 during the rest of the season. Marcel projects Ojeda to create only 44.33 runs (although we can up this number somewhat under the assumption that Ojeda will get more at bats than Marcel thinks).
Wouldn't it be nice if there was some way to manipulate the team so that, rather than replacing the solid bat of Chad Tracy, or letting Justin Upton go to waste on the bench, the Diamondbacks could avoid starting Augie Ojeda every day?
Enter Mark Reynolds. Although he is entrenched as the Diamondbacks's third baseman, Reynolds played shortstop during several years in the minors. While it's never easy to ask anyone to move from third base to second base, it's a legitimate question to wonder if Reynolds, a former shortstop, could do it.
If Reynolds can do a passable job at second base, Adam Dunn could, in effect, replace Augie Ojeda: Dunn would play left field, moving Conor Jackson to first, Chad Tracy to third, and Mark Reynolds to second. Dunn's 94 runs created would replace Ojeda's 44 (well, probably more like 50) runs created, good for four whole wins. That's a huge upgrade over two months of the season. Furthermore, the Diamondbacks could choose to play Ojeda at second and sit Tracy in games in which Brandon Webb pitches; in these games, infield defense is especially important, and the Diamondbacks don't have to worry as much about scoring runs.
Of course, four wins may be overstating the case: Dunn is a bad left fielder, and Reynolds may not be very good at second base, negating some of the value of this move. Furthermore, Dunn's Marcel projection assumes that he will be playing in the Great American Park, rather than Chase Field - although this change won't be too bad, as Chase Field is an excellent hitter's park as well as the GAB.
A conservative estimate would be that Adam Dunn is worth two more wins than Augie Ojeda, when considering the downgrades in defense. However, if Reynolds can do a decent job at second base, Dunn might end up being worth 3-4 wins. If Dunn ends up replacing Tracy, the upgrade is worth maybe one win.
If the Diamondbacks can manipulate their roster correctly, Adam Dunn could be worth a heck of a lot to them during the rest of the season. I have no idea if Mark Reynolds can play second base, but it behooves Arizona to find out.