The Prospect Bust Rate by Tool

The Five-Tool Scale Was Built for a Different Game

The 20-80 scouting scale grades five tools: hit, power, speed, arm strength, and fielding. Each tool is evaluated independently on a bell curve where 50 is average and 80 is elite. A prospect graded 60 hit / 55 power / 70 speed / 50 arm / 55 field looks balanced on paper. Scouts call that a five-tool player.

The problem is that the five tools carry different shelf lives and different translation rates to MLB production. A 70-grade speed tool in the minors often translates to a 50-grade speed tool in the majors within two years as the player adds muscle, ages out of peak sprint time, or faces pitchers who hold runners better. A 60-grade hit tool at age 21 often improves at the next level because pitch recognition refines with repetition.

The scouting scale treats all five tools as equal currencies. They are not. Some appreciate. Some depreciate. The exchange rate between minor league grades and major league value varies by tool, by age, and by era.

A "bust" here means the prospect never accumulated 5.0 career WAR within six years of their first top-100 ranking. That threshold is generous. It takes about one season of above-average play to reach it. More than a third of elite prospects fail to clear that bar, and the failure rate depends heavily on which tool got them ranked.

100 Prospects Enter. How Many Produce?

Take 100 top-100 prospects from preseason rankings between 2010 and 2020. Group them by their primary scouting tool. Follow each group for six years. Count how many become productive major leaguers (5+ WAR), how many become role players (1-5 WAR), and how many wash out entirely (below 1 WAR).

The gap opens wide at the 5+ WAR threshold. Hit-tool prospects convert at 65%. Speed-first prospects convert at 45%. By 10+ WAR, hit-tool prospects produce elite players at double the rate of speed-first ones. The tool that gets a player on the top-100 list shapes his probability curve for the next decade.

Speed Has the Shortest Half-Life

Sprint speed peaks between ages 22 and 24 for most athletes. By age 28, the average player has lost 0.3 seconds on his home-to-first time. That sounds small. In practice, it turns infield singles into outs, turns stolen base threats into station-to-station runners, and turns range in center field into a corner outfield assignment.

Baseball Reference tracks aging curves for every component of WAR. Baserunning runs peak at age 24 and decline steadily. A player worth +5 baserunning runs at 24 is typically worth +1 at 28 and negative by 30. Fielding runs follow a similar curve, because speed underpins defensive range.

A player who profiles on speed needs to develop secondary skills before the speed erodes. If he reaches the majors at 23 with a 70-grade run tool and a 40-grade hit tool, the clock is already ticking. He has roughly four years to learn to hit before his primary value disappears. Most do not learn to hit on that timeline.

The hit tool works in reverse. Contact ability and plate discipline typically improve through age 27. A 60-grade hit tool at 21 can become a 65 by 25 as the hitter learns to recognize spin, lay off borderline pitches, and adjust his timing to major league velocity. The tool appreciates with experience. Speed does not.

Raw Power Ages Better Than You Think

Power sits between hit tool and speed on the depreciation curve. Raw power, measured by bat speed and maximum exit velocity, peaks between ages 25 and 28. Game power, measured by home runs per fly ball, often peaks later because it also depends on launch angle optimization and pitch selection, which improve with experience.

The 45% bust rate for power-first prospects reflects a specific failure mode. Raw power without enough hit tool produces a player who mashes in batting practice, hits 25 home runs when he connects, and strikes out 200 times because he swings through pitches he should take. The power exists. The approach does not.

The star rate column tells the most important story. Hit-tool prospects produce stars (15+ career WAR in six years) at 22%. Speed-first prospects produce stars at 8%. That means you need roughly three speed-first top-100 picks to match the star probability of one hit-tool pick. The variance is extreme for what the scouting scale treats as equivalent grades.

Arm and Glove Grade High, Produce Low

Arm strength and fielding ability are real skills. They prevent runs. They have value. But the scouting scale overweights them relative to their contribution to wins.

Defensive WAR is capped by the structure of the metric. A Gold Glove shortstop at peak fielding might earn +2.5 defensive WAR in a season. An average shortstop earns 0. The spread is 2.5 wins. On offense, the spread between an MVP-caliber hitter and a replacement-level bat is 6-8 wins. The ceiling on defensive value is structurally lower than the ceiling on offensive value.

A prospect graded primarily on arm or glove needs to hit enough to stay in the lineup. If his bat never develops beyond replacement level, his defensive value produces a 1-2 WAR player. That is a useful bench piece or a late-inning defensive replacement. It is not a return on a top-100 prospect pick.

The 48% bust rate for arm-first prospects and 51% for fielding-first prospects reflect this math. The tool keeps them in professional baseball. It rarely carries them to impact production. Scouts see a cannon arm and fall in love. The arm is real. The WAR is limited.

The Market Has Started to Price This

The best front offices already weight tools differently when building their prospect rankings. The Dodgers, Rays, and Astros have historically overinvested in hit-tool and power-tool prospects relative to speed-first players. Their internal prospect boards look different from the public consensus lists.

International signing patterns reveal the preference clearly. Bonuses for hit-tool teenagers in the Dominican Republic and Venezuela have inflated faster than bonuses for speed-tool players over the past decade. A 16-year-old with advanced bat-to-ball skills now commands $3-5 million in signing bonus. A 16-year-old who runs a 6.4 sixty-yard dash but swings through breaking balls gets $500,000.

The draft tells a similar story. College hitters with polished hit tools go in the first round at higher rates than college athletes with elite speed but unrefined swings. In the 2023 and 2024 drafts, 7 of the top 10 picks were players whose primary tool was hit or power. Speed was the primary tool for zero of them.

The market is correcting. Slowly. Public prospect lists from Baseball America, FanGraphs, and MLB Pipeline still weight speed and defense heavily in their rankings because scouts trained on the five-tool framework continue to grade those tools at face value. The gap between how front offices value tools internally and how public rankings display them creates an information edge for teams willing to trust the data.

A Weighted Scale Would Change Everything

If the scouting scale reflected translation rates, a 60-grade hit tool would carry more weight than a 60-grade speed tool. One simple adjustment: multiply each tool grade by its historical WAR translation coefficient before summing the overall future value grade.

Using the data from 2010-2020, the coefficients look like this: hit tool at 1.0 (baseline), power at 0.72, speed at 0.45, arm at 0.63, fielding at 0.51. A prospect graded 60 hit / 50 power / 70 speed / 50 arm / 50 field currently gets a raw tool average of 56. With weighted translation: 60 + 36 + 31.5 + 31.5 + 25.5 = 184.5, divided by 5 = 36.9 weighted tool average. The speed-heavy profile deflates when you account for shelf life.

Compare that to a prospect graded 60 hit / 60 power / 45 speed / 50 arm / 50 field. Raw average: 53. Weighted average: 60 + 43.2 + 20.25 + 31.5 + 25.5 = 180.45, divided by 5 = 36.1. Almost identical to the speed prospect, despite looking worse on the traditional scale.

Sources & Data

Jesse Walker

Jesse Walker writes about baseball through data. He played outfield in high school, found his real position behind a spreadsheet, and hasn't stopped building models since.