The Misguided Lure of the Stolen Base


Let me start out by saying that in my opinion the stolen base is one of the most exciting plays in baseball. It’s a brief moment of breathtaking intensity in the midst of a game that can sometimes appear almost leisurely. And yet the value of the stolen base goes far beyond the infusion of energy it provides to players and fans. Baseball is a game of very small margins, and when successful a stolen base can put a team in a much better position to score a run and win a game.

However, it is critical to keep in mind the two-word phrase I slipped into the previous sentence - "when successful". Base stealing is extremely difficult, and often a split-second can be the difference between success and failure. In fact, so far in 2015 more than 30% of all attempted stolen bases have ended in failure. Additionally, the risk is two-fold since a "Caught Stealing" not only adds an out but also eliminates a valuable baserunner.

Let’s dive in to some statistics. Baseball Prospectus provides us with a wonderful table (updated daily) showing the "Expected Runs" value for every possible offensive situation. For example, this season an average team has the expected run value of 0.4677 at the start of each inning, when there are zero outs and no baserunners. This table will help us to determine exactly how valuable stolen bases really are, and also how risky.

2015 Expected Run Table

To start off, let’s focus on one very specific scenario. In our hypothetical situation, the leadoff man (let's call him Austin Jackson) has reached first base and our team's expected runs for the inning has therefore increased from 0.4677 to 0.8344. Now, let’s say you’re Lloyd McClendon, and you get to make the call on whether or not you put the steal sign "on" for Austin. You also know that AJ has stolen seven bases this year and has been caught only six times, for a 54% success rate. Now, I really doubt that Lloyd would have any idea what to do with our table, but let’s suspend disbelief for a second and take a look. If Jackson successfully takes second base, we have upped our expected runs total from 0.8344 to 1.0661, an increase of 0.2317! Wow, terrific! Jackson is more likely to succeed than to fail, and his success will significantly increase our chances of scoring. Therefore, we (Lloyd) should put the "steal" sign on, right?

Well, let’s see what happens if Jackson is thrown out at second. The end result would be one out and nomen on base, so our expected runs for the inning would decrease from 0.8344 to 0.2473. That’s a reduction of 0.5871! Oh no. Oh geez. That loss of 0.5871 expected runs for a Caught Stealing (CS) is more than 2.5 times as much as the 0.2317 increase we get from a Stolen Base (SB).

Because of this phenomenon, baseball writers/analysts/experts Michael Wolverton and Joe Sheehan (among others) created the following rule of thumb in the early 2000s: "If you’re stealing bases at less than a 75% success rate, you’re better off not going at all."

As with most rules-of-thumb, the exact numbers are slightly different and change based on the season and the specific situation. For example, the lowest required success rate is in a situation where a player is attempting to steal third base with one out. And if you think about it, this makes sense. With only one out, a runner on third can score on a ground ball to the right side, or on a deep fly ball, or even on a bunt up the third base line. None of these events would score a player from second base. At this point in the 2015 season, the required SB success rate for a steal of third base with one out is 68.2%, while the exact SB success rate for the situation we described earlier (runner on first, no outs) is 71.7%. For all stolen base situations combined, I have calculated that for this season the required SB success rate is 71.1%. Again, this number means essentially that if you’re stealing bases at less than a 71.1% success rate in 2015, you’re hurting your chances, not helping them.

Does anyone want to guess what the Mariners SB success rate is so far this year? It’s 50%. As of this morning, the M’s have attempted 46 stolen bases and have been successful on only 23 of them.


As you can see, this rate is good enough for 15th in the AL and 29th in the entire MLB, better only than the Dodgers and slightly worse than the Nationals. Wait a second though, you might be saying, if the 28th and 30th place teams in SB success rate are good clubs like the Nationals and Dodgers, there must be no correlation between this statistic and actually winning games. Well first of all I want to remind you, good sir, that a baseball team can have overall success without excelling at every aspect of the game, especially something as relatively minor as stealing bases.

However, if you examine these statistics a little more closely you’ll find a distinct difference between the Mariners and the Nationals/Dodgers. The thing is, the managers for the Nats and Trolley-Dodgers understand that their teams aren’t good at stealing bases, and because of this Washington and LA are 30th and 28th in the MLB in steals attempted. Our beloved M’s on the other hand are 4th in the American League and tied for 10th in the MLB.

This chart shows the Stolen Base success rates for all 30 MLB teams, sorted left to right by the number of attempted steals. I’ve also included a red line showing the 2015 overall required success rate (71.1%) and a trendline which confirms for us that in general teams who experience more success stealing bases tend to make more attempts. There is a bit of noise around the trendline, obviously, but no data point stands out more emphatically than the Mariners.

SB Success Rate by Attempts

There has been a lot of deserved criticism coming at Jack Z lately for the way he composed this Mariner team. He filled the roster with a bunch of slower, stronger guys who strikeout a lot, walk rarely, and hit a decent number of dingers. But this failure we’re currently examining is not the GM’s doing. All blame for this oversight should fall entirely on Lloyd McClendon and his misunderstanding of basic baseball concepts. He is employing an aggressive baserunning strategy with a team full of poor baserunners. Even the guys with some speed on this team (Miller, Ackley, Jackson, Bloomquist) have not had any recent success stealing bases. The primary job of a Major League manager is to get the best out of the team he has. Lou Pinella didn’t ask the 1997 Mariners to focus on small ball, and Ned Yost didn’t ask the 2014 Royals to swing for the fences. If someone with a direct connection to Lloyd happens to read this, PLEASE, tell him to just cut it out.

Let’s take a look at one more distasteful aspect of this situation. I did some calculations stemming from "Expected Runs" table we looked at earlier, and keeping in mind the frequency that each of the various stolen base situation tends to occur, I found that on average, a successful stolen base adds ~0.185 expected runs while being caught stealing negates ~0.455 expected runs. By multiplying these factors by the number of SB and CS for each team, I was able to calculate the total impact of stolen bases (in net expected runs) for all 30 MLB team.** As you can see in the table below, Toronto has been terrific this season, adding 4.1 net expected runs through stolen bases. Twelve other teams have also added value this season through their base stealing strategies. On the very bottom of this chart, I’m sure it’s no surprise by now that you’ll find Seattle, a full 2 runs below the next team at -6.2 runs negated thanks to Llyod & Co.’s ridiculously overly-aggressive stolen base strategy.

Net expected runs

Do you know how many games the Mariners have lost by a single run this year? It’s twelve…
Let’s say that the Mariners were just an average team at that their net expected runs were 0.0 for stolen bases. Do you think those six runs could have helped win some of those games?? Even if those six runs just changed the outcome in 4 games, Seattle’s record would be 29-28, instead of 25-32. That’s a huge difference!

So now I’ve written a lot about stolen bases, and I know that really…it’s not the only thing wrong with this team. But it’s something that, in my opinion, could be quickly and simply rectified. Stop trying to steal bases! It’s not worth it! Or if you can’t resist the lure, Hey Lloyd!! you can DFA Weeks, promote James Jones and have him pinch run every time you get the urge.

**Calculated Expected Runs Added (XRA), Expected Runs Lost (XRL) and Net Expected Runs (NetXR) were calculated based on assumed averages for how often each type of stolen base occurs, since team-specific actuals were not easily available