The tBGR base running stat (total Bases Generated as a Runner) is based on the bases gained or lost by base runners on plays in which the batter does not move the runner. That includes plays like stolen bases, caught stealing, pickoffs, errors on pickoff attempts as well as advances like bals, wild pitches, pass balls, runner hit by batted ball, runner interferences, and a few other plays. None of those plays involve a batted ball. But after seeing extra bases taken stats on other baseball stat sites, we realized that base running is more than just the 15 plays we include in tBGR. So we decided to develop our own extra bases taken stat called Xtra Bases. While not strictly within the conventions of tBG, we add this new stat to tBGR to create a stat called XtBGR, which is one of the most comprehensive base running stats available.
We define an "xtra base" as simply one or more bases advanced by the runner in addition to the base(s) generated by the batter. Example: a runner advancing from 1st to 3rd on a single. The batter provided one base with the single, but the runner moved up two bases. And there's one additional criteria: the runner advance is not forced. If forced, the xtra base is not counted.
We apply this approach to base hits, tag ups, and groundouts. Here are the plays we count as extra bases. The codes for each play appear on our reports:
- Sngl1-3 - Runner advances from 1st to 3rd (or to Home) on a single
- Sngl2-H - Runner advances from 2nd to Home on a single
- Dbl1-H - Runner advances from 1st to Home on a double
- FlyO1-2 - Runner advances from 1st to 2nd (or to 3rd or Home) on a fly out.FlyO2-3 - Runner advances from 2nd to 3rd (or to Home) on a fly out.
- FlyO3-H - Runner advances from 3rd to home on a fly out.
- GrO2-3 - 1st base empty. Runner advances from 2nd to 3rd (or to Home) on a ground out.
- GrO3-H - 1st or 2nd base is empty. Runner advances from 3rd to Home on a ground out.
Note that in some cases we count an advanced of two extra bases as one extra base. That is because the additional extra base is almost always the result of an error or a throw to a different base. Therefore, the additional base is not an actual extra base gained by the base runner as we define it.
Also, note that on fly outs and ground outs, the batter is out and, therefore, generated zero bases from his plate appearance. However, in each case, the runner moved up one base, one more than the batter provided.
Also note that we count extra bases on ground outs only if the base runner is not forced to run. That’s why we don’t count an advance to 2nd on a ground out. In that play, the runner is forced to run. That also explains why the GrO2-3 is counted only if 1st base is empty and GrO3-H is counted only if 1st or 2nd base is empty. Both conditions indicate that the runner wasn’t forced to run.
We
also have three Xtra Base reports:
Xtra Bases Player Season: Most Xtra Bases in a season: Augie Galan, 1935, Chicago Cubs: 113 Xtra Bases
Xtra Bases Player Career: Most Xtra Bases in a Career? Rickey Henderson with 1,499. Pete Rose is 2nd with 1,317, and Ty Cobb is 3rd with 1,152. But our tBG database goes back only to 1911, so the total for Cobb is incomplete because he started playing in 1905. With another six years of Xtra Bases, it’s possible that Cobb would surpass Henderson for the all time career lead. Cobb averaged 64 Xtra Bases per season, so another six seasons at that average would put him at 1,536, ahead of Henderson.
Xtra
Bases Player Team Season: Most Xtra Bases in a Team Season? Detroit
Tigers, 1934. 650 Xtra Bases. Not surprisingly, this team was managed
by Ty Cobb. Also, of the top 100 team seasons, 86 of them are for seasons
between 1921 and 1939, the Golden Age of extra base advancing, apparently.
Also note that base running stats developed by Baseball Prospectus and
Fangraphs are more sophisticated because they incorporate extra bases
not attempted and extra base attempt outs.