The Diamondbacks’ Baserunning Woes

The D-backs did some things really well last season. Baserunning was not one of those things. The D-backs were dead last in terms of how they affected games with stolen base attempts, but they also weren’t particularly good at other aspects of baserunning, either.

First, a quick look at how the D-backs fared overall. The “BsR” component of WAR combines effectiveness in stolen base attempts and other aspects of baserunning (more on that below). In baserunning runs (BsR), the D-backs were -10.5 as a team (26th in MLB) — the equivalent of about a full win below average. The Tigers (-19.4), they were not. But with all of the other efforts toward marginal improvements this offseason, you can tell why Steve Sax got sacked (say that three times fast).

I’m looking mostly at BsR and its main components below, but it was not the only statistic to rate the D-backs poorly — Baseball Prospectus keeps its own statistics on base running, and in Baserunning Runs (BRR), the D-backs finished -9.7, good for just 28th in MLB.

Stolen Base Attempts

Baserunning statistics don’t distinguish between foot speed and good decision making, and for good reason — that doesn’t matter. But we can look at baserunning in between batted ball events separately from what happens when a ball is in play. Stolen base attempts are those events that happen in between batted ball events.

For stolen bases, FanGraphs uses “wSB,” a number equivalent to runs that factors in stolen bases and caught stealings. This is where the Diamondbacks were outright horrible: they put up a -8.6 mark, more than a run worse than any other team. And it doesn’t take a genius to figure out why (fortunately for me): the team attempted steals 103 times, but was caught stealing 41 times. That’s a terrible 60.0% success rate. That, too, was worst in the majors — and at least the next worst teams (Twins, 61.2%; Tigers, 63.6%) had the sense to try less often (Twins 85, Tigers 55).

You probably guessed this already, but it was Gerardo Parra leading the charge in the wrong direction, with -2.4 wSB all to himself. Still, of the 14 D-backs players with at least 100 PA last season, the only two that posted positive numbers were Cliff Pennington (0.1 wSB) and A.J. Pollock (0.9). Even Adam Eaton was caught twice in seven attempts. The D-backs’ new full time position player, Mark Trumbo, also had a negative number (-0.2 wSB). So for the love of whatever, let’s give Pollock the green light, but shut down the rest of the running game unless the team shows some improvement.

Other Baserunning

The other component of BsR is Ultimate Base Running (UBR), which measures the effect of things like success advancing from first to third on a single. The process uses the difference in run expectancy to assign a run value; in the first to third example, UBR uses the difference between the expected run value of first and third (with X number of outs) against the expected run value of first and second (same number of outs). As Mitchel Litchman has explained, it’s the same type of process that Ultimate Zone Rating (defensive statistic) uses to assign run values to outfield arms (if a runner doesn’t go from first to third on a single because Parra fielded the ball, Parra gets some credit for that).

In UBR, the Diamondbacks fared much better: pretty close to average with -1.9 (20th in MLB). Running the bases still was not a strength for the D-backs, but it wasn’t really a liability, either. Eaton led the way (in limited playing time) with 3.4 UBR, more than three runs’ worth of value in how he ran the bases other than with base stealing. And Gerardo Parra is no longer the goat — his 1.5 UBR was at least a positive number. It was Martin Prado (-2.9 UBR) and Cody Ross (-2.5 UBR) who did the most damage, either because they were making poor choices on the base paths or because they just weren’t very fast.

Just like batting average accurately records a result but also is the result of some luck, wSB is firmly rooted in what actually happened on the diamond. UBR, however, relies on the idea that some averages will even out (not all outfield singles represent equal chances to go first to third, for example). So while UBR is helpful, we’d probably have to look at larger samples (three years?) to draw conclusions about the skill of particular players. Prado has a positive number for his career (4.6 UBR) and Ross does too (3.6 UBR), so we may be looking at some bad luck.

Another thing we might be seeing, though, is a coaching problem. Not just in terms of how players are trained, but in terms of things like sending runners home. There’s at least a shadow of a doubt about whether Matt Williams was a good third base coach — especially when you consider that Prado and Ross were in their first year with the D-backs last season. But to really throw Williams under the bus, we’d have to do some more research.

What we do know, however, is that the D-backs have some room for improvement. And if they turn this significant baserunning negative into any kind of positive, it might make a difference of one or two wins.

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Here’s a table of the D-backs’ totals for UBR, wSB, and the overall BsR score, which is a total of the two. Plate appearances aren’t an exact indication of how often each player was on the base paths, but I include it as a general guide. All three of UBR, wSB and BsR are counting stats, not rate stats — meaning that the numbers below do not necessarily mean that Martin Prado was worse on a rate basis than, say, Wil Nieves. I’ve also included Mark Trumbo for the fun of it.