Frankly, the Arizona Diamondbacks' infield defense was terrible last season. Orlando Hudson (uncharacteristically) and Stephen Drew each posted the worst Revised Zone Rating (percentage of plays made on balls hit to their zone) at their positions among all starting middle infielders. Mark Reynolds "only" finished sixth worst in RZR among major league third basemen, but ranked first in errors at any position at 34, first in throwing errors at any position at 18, and last in fielding percentage at any position at .904.
This simply doesn't cut it when the ace of the Diamondbacks' staff induces more ground balls than any other pitcher in baseball and a greater percentage of ground balls than any other major league starter. It's amazing that Brandon Webb was able to finish second in Cy Young balloting when his infielders let him down time and time again, and if the Diamondbacks don't shore up the defense behind him, he will have little reason to give the Diamondbacks a hometown discount in upcoming contract negotiations.
Enter the prospects. While the Diamondbacks do not have any infield prospects ready to make an impact in 2009 (save for Joshua Whitesell at first base), several could factor into the 2010 equation. The Diamondbacks will exercise their club option on Webb for 2010, and if no deal has been reached by then, a commitment to infield defense could persuade him to stay. On the other hand, he's a near-lock for a Cy Young Award with a good defense behind him, so it may behoove the Diamondbacks to negotiate a deal before installing an improved infield defense.
The arm, of course, is only half of the defensive equation, and far more important for third basemen and shortstops than it is for second baseman. It hardly matters at all for a first baseman. But it does have some key functions. A third baseman with an exceptional arm can dissuade against bunting for a base hit. A shortstop with a plus-arm can play closer to the bag , as they will be able to throw runners out going deep into the hole to their right. A second baseman with a good arm will turn more double plays than one with a weak arm.
Here are the FutureBacks infield arm rankings, taking into account both the strength and the accuracy of the prospects' throwing arms. Listed along with each player is their 2008 positional breakdown with some rudimentary fielding metrics (RFg = Range Factor per games played, or putouts plus assists divided by games).
1. Pedro Ciriaco (SS: 87 G, 250 A, 20 E, 44 DP, .949 FP, 4.30 RFg) (2B: 38 G, 141 A, 3 E 30 DP .985 FP, 5.34 RFg)
Ciriaco has held the title of "strongest infield throwing arm in the organization" for years, but this is the first season that he has been able to throw it accurately with any consistency. He had been able to beam it over towards first base no matter what position his body was in - lying on the dirt, running towards the hole, on one knee - due to his freakish gun. Unfortunately, he should not have thrown the ball in many of those instances, either because he was rushing when he had plenty of time or because he had no real chance to make the play. Although his accuracy still grades as below average, it is no longer horrendous, as he is more consistently setting his feet and angling his body properly for his throws. The strides that he has made this season give us the hope that he will continue to improve and one day flash one of the most impressive infield arms in the majors.
2. Yunesky Sanchez (SS: 100 G, 277 A, 14 E, 62 DP, .969 FP, 4.33 RFg) (2B: 16 G, 44 A, 1 E, 9 DP, .987 FP, 4.63 RFg)
3. Taylor Harbin (2B: 87 G, 240 A, 7 E, 51 DP, .983 FP, 4.52 RFg) (SS: 43G, 120 A, 13 E, 25 DP, .937 FP, 4.51 RFg)
Harbin essentially has the same combination of solid arm strength and good accuracy from second base that Sanchez exhibits from the shortstop position. Harbin can play shortstop as well, but there his arm strength grades out as just average. That's just fine, as there is obviously a greater immediate need for second baseman than shortstops in the organization right now. In fact, don't be surprised if Harbin pulls a Yunesky and skips over Hi-A to work as the BayBears' primary second baseman in 2009. That would put him in position to possibly take over the major league reigns in 2010, as the D-backs appear to be looking for a mere stopgap in the 2009 season.
4. Antonio Sepulveda (SS: 33 G, 91 A, 21 E, 12 DP, .870 FP, 4.27 RFg) (2B: 10 G, 23 A, 2 E, 4 DP, .958 FP, 4.60 RFg)
Sepulveda's arm is as strong as Ciriaco's is, but probably just as erratic as Ciriaco's was at the same age. Sepulveda supposedly doesn't turn 17 until New Year's eve, but even if that isn't 100% accurate, he is very talented, very young, and very raw. At just 5'9" and 150 pounds, you have to wonder how Sepulveda manages to get the ball all the way to the first baseman, much less whip it there at a higher velocity than 95% of professional infielders. The key for him may be to put a little less effort into his throws, sacrificing some of the velocity for a bit of accuracy. Minor league field coordinator Jack Howell named him the Most Improved Position Player during Instructs, and considers his arm to already rank as the best in the system. We're comfortable ranking him fourth now, realizing that he could jump up to #1 if he continues to progress.
5. Clayton Conner (3B: 12 G, 21 A, 7 E, 0 DP, .811 FP, 2.50 RFG)
Like Sepulveda, Conner gets ranked here entirely due to arm strength. He is still honing his defensive craft, and the fact that he missed most of the 2008 season with injuries certainly did not allow for much improvement. Most of the strides that he made defensively came last fall during Instructs, but they were enough for Conner to make a few spectacular plays this April. He only turned 22 in October. Therefore, much like his raw power, he still has time to turn that raw arm strength into a plus tool. He has the strongest hot corner arm in a system lacking great defensive third basemen, though Kyle Greene has the potential to overtake Conner next year.
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