What is BsR? Definition, Formula, and Example
BsR (Base Running Runs) is FanGraphs' all-in-one baserunning metric that measures how many runs a player adds or costs his team on the bases — including stolen bases, extra-base advancement on hits, and double-play avoidance — relative to a league-average runner.
Plain-English Definition
BsR — short for Base Running Runs — is FanGraphs' umbrella metric for everything a player does on the bases. Unlike raw stolen-base totals, BsR captures the *full* offensive value of baserunning: did the runner go first-to-third on a single, did he score from second on a soft groundball, did he avoid getting doubled up, did his steal attempts actually generate runs given the league-average breakeven rate of roughly 75%? BsR rolls all of that into a single runs-above-average number. Zero is league average. Plus-5 is a real weapon. Anything north of plus-7 in a full season is elite — usually a top-10 finish.
How BsR Is Calculated
BsR is the sum of three independently calculated components:
BsR = wSB + UBR + wGDP
- wSB (Weighted Stolen Base Runs) — Stolen bases and caught stealings converted into runs using linear weights, then compared to league-average SB attempt rate. A steal is worth about +0.2 runs; a caught stealing is worth about –0.4 runs.
- UBR (Ultimate Base Running) — Non-SB advancement value: scoring from second on a single, taking an extra base on a flyout, avoiding an out trying to stretch, advancing on a wild pitch or passed ball. Each opportunity is scored against the league-average advancement rate for that game state.
- wGDP (Weighted Grounded Into Double Play) — Runs added by avoiding double plays in DP situations, adjusted for the league-average GIDP rate in identical contexts. Slow runners with high contact rates bleed value here.
Worked Example
In 2024, Bobby Witt Jr. posted a +7.6 BsR — roughly +3.0 wSB, +4.0 UBR, +0.6 wGDP. He stole 31 bases at an 86% success rate (well above the league breakeven), regularly went first-to-third on singles, and rarely got doubled up. That +7.6 translates to nearly a full win of value from baserunning alone.
On the other end, Salvador Perez finished 2024 at roughly –5.8 BsR. He stole zero bases, station-to-statianed his way around the diamond, and grounded into 27 double plays. That's about half a win *lost* on the basepaths — a hidden cost that batting average and slugging never show.
League leaders in BsR are usually Witt, Trea Turner (+5 to +7 every year), Ronald Acuña Jr. (+7.4 in 2023), and Corbin Carroll. Bottom dwellers are consistently catchers and slow corner sluggers.
Why BsR Matters
For front offices, BsR is the cleanest single number to evaluate "how much does this guy hurt or help us on the bases?" — far better than SB totals, which ignore CS damage and miss 80% of baserunning value. For fantasy and DFS, BsR-positive players outperform their stolen-base projections because they score more often from second and third. For trade evaluation, it surfaces value that traditional stats hide.
Limitations and Misconceptions
BsR is not a speed metric — sprint speed measures raw athleticism; BsR measures *runs created* from baserunning *decisions*. A player can have elite sprint speed and mediocre BsR if he gets bad reads or runs through stop signs. UBR also has opportunity bias: a hitter batting in front of high-OBP teammates simply has more chances to score from second.
It also undervalues the *threat* of speed — pitchers throwing from the stretch, pickoff attempts, infield holds — which shows up in the hitter's stats, not the runner's BsR.
Related Terms
In Legends Deck
BsR feeds directly into the Baserunning Rating on every Legends Deck card alongside sprint speed and stolen base success rate. A Bobby Witt Jr. card will out-advance an equivalent-speed Salvador Perez card on simulated singles to the outfield and avoid simulated double plays at a higher rate — exactly how the real BsR gap plays out across a full season.