Pull up any modern defensive leaderboard and you will run into two numbers that claim to measure the same thing and refuse to agree on it. One is Outs Above Average (OAA), the range metric Statcast built from tracking data. The other is Defensive Runs Saved (DRS), the older, broader system from Sports Info Solutions. Both are expressed in roughly the same currency — runs above or below an average fielder at the position — and both will happily tell you a given shortstop was worth, say, a dozen runs with his glove. The trouble starts when one says +12 and the other says +4.

That gap is not a bug; it is the natural result of two systems measuring defense through different lenses. Understanding why they diverge — and which one to trust for which question — is the difference between reading a fielding number and being fooled by one.

What OAA measures, briefly

OAA is fundamentally a range metric, and its engine is catch probability. For every ball put in play, Statcast knows where the fielder started, where the ball was headed, and how much time connected the two. From those inputs it estimates the probability that an average fielder makes the play, then credits the defender the difference between the outs he actually recorded and the outs he was expected to record. Convert a 30% play and you bank most of an out; let a routine 95% play drop and you are charged for it. Sum every chance over a season and you have OAA. We cover the full construction in our explainer on Outs Above Average; the key point here is its scope. OAA, in its core form, is about getting to the ball — range and the conversion of difficult chances into outs.

Statcast also translates those outs into runs as Fielding Run Value, since a robbed double prevents more damage than a converted routine grounder. That run-denominated version is what lets OAA sit next to DRS on the same axis and be compared at all.

What DRS measures, briefly

DRS is older and deliberately broader. Where OAA is built almost entirely on tracked range, DRS is a charting-based system that bundles several distinct defensive skills into one runs figure. Its range component — historically the largest piece — leans on charted hit locations and zone-based estimates of where an average fielder would have reached. But DRS does not stop at range. It folds in a fielder’s throwing arm (especially for outfielders gunning down baserunners), his contribution to turning double plays, the prevention of errors, and adjustments for how a player was positioned before the pitch.

The upshot is that DRS tries to answer a wider question. OAA asks, “How many outs did this defender produce beyond expectation, given the balls hit near him?” DRS asks something closer to, “Adding up range, arm, double plays, and the rest, how many runs did this defender save or cost his team?” Those are related questions, but they are not identical, and the answers will not always line up.

Why the two numbers diverge

Start with the inputs. OAA is built on measured tracking data — the actual start point, the actual hang time, the actual distance covered. DRS historically leans more on video charting and zone models, asking trained charters to log where balls landed and inferring makeability from that. Tracking and charting are different instruments, and different instruments produce different readings even when pointed at the same skill.

Then there is scope. Because DRS includes arm, double-play work, and other components that OAA leaves out, a player can grade very differently in the two systems for entirely legitimate reasons. Picture an outfielder with merely decent range but a cannon for an arm who routinely freezes runners and throws out the ones who test him. OAA, which is not built to reward arm strength, might peg him as roughly average. DRS, which explicitly credits outfield arm, could rate him well above average. Neither metric is wrong — they are simply measuring different bundles of defense.

Positioning is the third and trickiest source of divergence. Both systems have to decide how to handle a fielder who was expertly placed by his coaching staff and therefore started a step closer to the ball. OAA evaluates from where the fielder actually stood, so good pre-pitch alignment tends to flow through as credit to the fielder. DRS has historically tried to separate team positioning from individual skill through its own adjustments. With infield shifts curtailed by rule in recent seasons, this matters less than it did during the shift-heavy era, but it remains a real reason two honest systems can disagree on the same defender.

How to read a defensive number

Whichever metric you are looking at, the scale is mercifully similar because both are centered on the league-average fielder. Zero is average — a defender who saved exactly as many runs as expected lands at 0, no credit and no blame. A few runs in either direction is ordinary noise and should not move your opinion of anyone. Something in the neighborhood of +10 over a full season marks a genuinely very good defender, the kind whose glove shows up in the standings. Figures climbing toward +15 or beyond start to describe elite, award-caliber gloves. The negative side mirrors it: a number well below zero flags a defender who is costing his team runs in the field.

A clearly-illustrative case makes the reading concrete. Imagine a center fielder — call him a hypothetical — who posts something like +14 OAA but only +6 DRS in the same season. That is not a contradiction to be resolved by picking a winner. The most likely reading is that his raw range was elite (OAA loves it), while one of DRS’s other components — perhaps a below-average arm, or a positioning adjustment that withholds some of the credit — pulled its broader figure down. The honest conclusion is “excellent range, with some question marks in the parts OAA does not see,” not “one number is right and the other is broken.” These figures are illustrative, chosen to show how a split is read; they are not a real player’s line.

Mind the sample

The most important caveat applies to both metrics equally: defense stabilizes slowly. Defensive chances accrue far more slowly than plate appearances — a fielder simply does not get enough hard plays in a month for either number to settle. A single month of OAA or DRS is mostly noise. Half a season is suggestive. Even a full year of fielding data carries more uncertainty than an equivalent slice of offensive data, which is why analysts lean on multiple seasons before declaring anyone’s glove great or terrible. When you see a defender with a wild fielding number in April, the responsible move is to wait.

This slow-to-stabilize quality is also why a one-season disagreement between OAA and DRS should rarely alarm you. Two noisy estimates of the same underlying skill will wobble apart in small samples and tend to converge as the chances pile up. Over several seasons, the two systems usually agree on who the standouts and the liabilities are, even when they quarrel about the exact figure in any single year.

The honest stance: use both

So which metric wins? The right answer is to refuse the question. OAA is the cleaner, more stable measure of pure range, built from physics rather than judgment, and it is the one to reach for when range is what you care about. DRS is the broader accountant, the one that remembers a strong outfield arm and a deft double-play pivot exist and matter. The sharpest read on a defender comes from holding both numbers up at once: when they agree, you can be confident; when they split, the split itself is information about which parts of the player’s defense are carrying the grade.

This is also the deeper reason the all-in-one value stats disagree. The major WAR models differ by site in large part because they make different choices about defense — one framework may build its fielding component on OAA and Fielding Run Value, another on DRS. When two WAR totals for the same shortstop diverge, the defensive input is usually the first suspect, and knowing how OAA and DRS are each constructed lets you judge for yourself which grade you trust.

The bottom line

OAA and DRS are two honest attempts to put a runs figure on the hardest-to-measure half of the game. OAA measures range from tracked geometry; DRS measures a broader bundle — range plus arm, double plays, and positioning — from charting. They diverge because they use different inputs and answer slightly different questions, not because either is broken. Read each on its near-identical scale — zero is average, +10ish is very good — respect how slowly defense stabilizes, and when in doubt, use both. The disagreement is not a problem to solve. It is the most useful thing the two numbers tell you.

Sources & Further Reading

  • Baseball Savant — Outs Above Average leaderboards and the catch-probability methodology behind Fielding Run Value.
  • FanGraphs — Defensive Runs Saved, its components, and the role of fielding metrics in WAR.
  • MLB.com — Statcast glossary entries for Outs Above Average and Fielding Run Value.