Ultimate Base Running (UBR) is FanGraphs’ way of accounting for the value a player adds to their team via base running. Much like UZR and wRAA, this value is determined using linear weights, with each individual base running event receiving a specific run value. Base running isn’t a huge part of the game, but taking the extra base and avoiding outs of the bases can add a few runs a year.
For more specifics on how the run value for each base running event is calculated, see Mitchel Litchman’s primer. According to Litchman, here are the different base running events that are accounted for in UBR:
1) On a hit, advancing an extra base, not advancing an extra base, or getting thrown out trying to advance an extra base, as long as no other base runner is blocking an advance.
2) A batter getting thrown out trying to advance an extra base on a hit (if he successfully does, we don’t know it, as he is simply awarded a double, for example, on a usual single where he advances an extra base).
3) On a hit, the batter advancing, not advancing, or getting thrown out when a runner is safe or out advancing an extra base.
4) Trailing runners advancing, not advancing or getting thrown out when a leading runner is safe or out trying to advance an extra base on a hit or an out. This is basically lumped together with #1 above.
5) Runners trying to advance on fly ball outs – i.e. tagging up.
6) As mentioned above, on ground balls to the infield, runners on first staying out of the force or DP at second base, whether the batter is out or is safe on a FC.
7) Also as mentioned above, a runner on second advancing or not (or getting thrown out) on a ground ball hit to SS or 3B.
Runners on third base advancing, not advancing, or getting thrown out at home on a ground ball are not considered (on air balls they are). Runner advances or outs on WP or PB are not considered either.*
Please note that the following chart is meant as an estimate. No matter the year, this statistic will always have zero UBR as league-average.
Things to Remember:
● UBR does not account for stolen bases and caught stealings, which are dealt with by wSB.
Links for Further Reading: