New-era outfield arms

With advanced defensive metrics capturing just over a decade-sized sample, the all-time leaderboard measuring outfield arms reads like a newspaper, providing a retrospective snapshot of what was. Although a handful of players within recent memory (and somewhat high-definition video) were known for their arms before the gift became quantifiable, a new decade has ushered in a host of outfield arms projected to inevitably join past greats.

Looking back (1992—2002):

Before advanced metrics allowed us to fully appreciate the effect an outfielder's plus-arm can have on a season's worth of games, we had outfield assists; however, assists fail to account for a host of critical facets marking the value of outfield arms — namely, the "don't run on him" effect. For the sake of quickly looking back, we neither need nor have formulaic complexities to select some of the pre-saber best hoses.

Larry Walker:

Credit: MLBAM

• 13 of 17 career years pre-2002 (154 career outfield assists, 0.09 assists/9)

Vlad Guerrero:

Credit: MLBAM

• 6 of 16 career years pre-2002 (126 career outfield assists, 0.08 assists/9)

Saber-Era Career Leaders (2002—2012):

Player	Innings	ARM	rARM	Assists	A/9
Francoeur	9854	62.9	48	116	0.11
Rios	10981	36.2	30	75	0.06
Edmonds	7513	30.7	22	57	0.07
Victorino	8291	27.7	34	59	0.06
Suzuki	14980	24.4	-1	93	0.06

In the decade-plus after advanced defensive metrics became measurable, a stable of players became known for consistency in the four-facet outfield arm package: clean fielding, quick release, arm strength and throw accuracy. While the development of UZR and DRS has allowed defensive value to become quantifiable, for outfielders each is comprised of an arm component (ARM & rARM respectively), keying in on where exactly a plus-arm provides value. When stripped to their bare components, both metrics function in essentially the same way, but to refresh your memory, I'll skate through the basic aspects of each.

Credit: SB Nation (Above: Jeff Francoeur)

UZR's ARM metric (or outfield arm runs) quantifies the amount of runs above average an outfielder saves with his arm. The metric evaluates baserunning outcomes on balls hit to the player (taking an extra base, getting thrown out attempting to do so, or holding), given where and how hard the ball is hit, and park factors. DRS's rARM (or outfield arm runs saved) distinguishes advances, kills and holds by the extra base being attempted (stretching a single into a double, going 1st to 3rd on a single, 2nd to home on a single, 1st to home on a double) and adds a fourth baserunning outcome, miscellaneous kills (runner thrown out without a base hit — usually on sacrifice flies). Similarly factoring in the batted ball, fly ball (FB), ground ball (GB), and miscellaneous kill (MK), runs saved are determined and combined for the final product.

New-Era Arms:

Looking forward, a group of young outfielders project to be mentioned among the league's best outfield arms — at least in the short -term. When qualifying a group of outfield arms "here to stay," there obviously exists an overlap where players in their prime have already established prominence in this category — so I'll distinguish between last year's top-five (by ARM) with more than five career MLB seasons through today without comment, and those with five or less (the Gerardo Parra line). This should provide a better look at the potential new-era of arms without any overlap.

5+ years — Top 5 (2013):

Player	Club	Innings	ARM	rARM	Assists	A/9
Gordon	KCR	1364	9.6	6	17	0.11
Jones	BAL	1394	6	7	11	0.07
Bruce	CIN	1438	5.9	4	13	0.08
Bautista	TOR	966	5.5	9	8	0.07
Gomez	MIL	1242	5.3	6	11	0.08

≤5 years — Top 5 (2013):

Player	Club	Innings	ARM	rARM	Assists	A/9
Lagares	NYM	904	13.8	11	15	0.15
Parra	ARI	1355	11.1	12	17	0.11
Aoki	KCR	1297	7.5	5	9	0.06
Martin	TEX	1127	6.5	6	14	0.11
Brown	PHI	1138	3.7	4	9	0.07

Credit: FanGraphs (Above: Juan Lagares)

While Parra approaches the transition into the category of well-established, three other notable young players have posted low-plus numbers, but have better reason to hang around in the conversation of those capable of becoming generational notables in this category of players. Both Bryce Harper and Yoenis Cespedes posted top-five ARM, and top-eight rARM numbers their rookie years (2012), but faded this past year in part due to struggles with injury. The third name (stats not listed below) is Yasiel Puig — not listed because his numbers lack adequate sample size. Puig's defense is raw, but he has shown potential league-best flashes of outfield arm lethality in less than 900 career innings.

Bryce Harper:

Harper	ARM	rARM	Assists
2012	6.2	5	8
2013	3	3	13

Credit: SB Nation

Yoenis Cespedes:

Cespedes	ARM	rARM	Assists
2012	6.8	5	9
2013	1.4	3	10

An obvious concern when looking at potential new-era outfield arms is their ability to stick around in their respective lineups — it's because of this that Harper, Cespedes and Puig tentatively comprise this group's core, despite statistically down arms this past year, and Lagares drops out despite a better arm. With Aoki projected to start in right for Kansas City, Dom Brown in left for Philadelphia, and Martin in center for Texas, this secondary group will remain eligible — aptly rounding out a projection of the league's A-1 outfield arms here to stay.

. . .

All statistics courtesy of FanGraphs and Baseball-Reference.

Joshua Mastracci is a contributor to Beyond the Box Score. You can follow him on Twitter at @joshuamastracci.