The D-Backs Are on the Brink of a New Stolen-Base Frontier

We do not live in an exciting time for record chases. Ichiro’s single-season hits record is perfectly safe, as is Barry Bonds‘ home run record. The records that are getting broken are of the team variety, and even those seem to be as much a sign of the times as they are reflective of a team’s historical excellence. The team home run record, for example, is about to fall for a second straight year, with the Minnesota Twins on pace to demolish the 2018 Yankees’ mark. The record for strikeouts recorded by a pitching staff has been broken in each of the last two seasons as well.

Still, there is at least one team record in jeopardy that’s worth a bit more discussion. In the first half of the season, the Arizona Diamondbacks stole 50 bases in 56 attempts, good for an 89.3% success rate. The all-time record, set by the 2007 Philadelphia Phillies, is 87.9%.

Is it the sexiest record in sports? It is not. Is that a jaw-dropping gap between the record pursuer and the current record holder? Nope! But I’m not here to talk about what it would mean if the D-backs edged the 2007 Phillies out by a decimal point or two at the end of the season. What I’d like to talk about instead is what it would mean if Arizona finished the year with a 90% success rate.

Before we talk about a 90% stolen-base success rate, let’s discuss an 80% success rate. Since the beginning of the live ball era, just 38 teams in major league history have finished a season with a stolen-base success rate of 80% or higher. Here are those 38 teams:

A few things jump out immediately. First, while the data pool stretches back to 1920, most teams listed here are from recent years. In part, that stems from our contemporary understanding of the value of a stolen base, an era in which nearly everyone recognizes that a 2-or-3-to-1 ratio of stolen bases to caught stealings is necessary for swiped bags to provide any value to a team’s offense. Even when stolen bases reached their nadir from the 1930s to the 1950s, running less frequently still did not seem to lend itself to running carefully.

It wasn’t until the 1975 Reds that baseball saw a team steal successfully on 80% of its attempts, more than 50 years after the live ball era began. That team — led by Joe Morgan (67 steals, 10 times caught stealing), Dave Concepcion (33 SB, 6 CS), and, interestingly enough, Johnny Bench (11 SB, 0 CS) — won 108 games and a World Series title. The next team to have an 80% success rate on stolen bases was pretty good too. The 1980 Kansas City Royals had seven players steal double-digit bags, and only one of them was caught more than seven times: Willie Wilson, who was thrown out 10 times while stealing 79 bases. The Royals won 97 games and the American League pennant.

Whether from pure athletic skill or innovative thinking, those teams established a new bar for how efficient a team could be when running the bases. Their success was not often replicated: only four other clubs converted at least 80% of their stolen-base attempts by the end of the 1990s.

Over the past 10 years, however, we’ve seen about two teams do it every season. An 80% success rate on stolen bases is historically great, but in modern times, it isn’t particularly notable. Going above 80%, however, is.

Look at that table again. Of the 38 teams who achieved an 80% success rate on stolen bases in a season, 17 — nearly half the sample — cleared the threshold by less than one percentage point. Not including the D-backs, only 11 clubs have recorded an 82% success rate, none since 2013. To hit 90% would be a significant accomplishment.

So, how is Arizona doing it? The answer starts with speed. Arizona has the single fastest player in baseball, according to Statcast’s sprint speed metric, in Tim Locastro. Locastro, 27, was traded twice over the offseason and is on his fourth team since being drafted by Toronto in 2013. He appeared in just 21 big league games before 2019, but he’s hit well throughout his minor league career while stealing bases at an 81% clip. He’s 7-for-7 this season, tied for the third-most steals without being caught in baseball.

Nick Ahmed is also perfect in six stolen base attempts, as is Ketel Marte in four. Neither of them burn the way Locastro does, but they’re both quick. Arizona’s best base-stealer has been Jarrod Dyson. Dyson has understandably lost a step from his once-elite speed, but he’s still in the 87th percentile as a 35-year-old, and as efficient on the bases as ever. He’s been successful nearly 85% of the time throughout his career, and is a tidy 20-22 in 2019.

Dyson is also the only D-backs player to be caught more than once this season; there are no reckless thieves dragging the rest of the team’s efficiency down. Further, the team doesn’t appear to be getting into trouble with big leads, as they’ve been picked off just three times all season. That’s the second-lowest total in baseball.

One shouldn’t take Arizona’s cautiousness for cowardice, as the club’s 50 stolen bases rank ninth in the majors this season. Here’s how they stack up against the other teams listed on the above table, with Arizona highlighted in yellow.

On this graph, you want to be as far down and as far to the right as you can be. No team did that better than the 2007 Phillies, who are highlighted in red. But no team in this sample has been caught fewer times on a per-game basis than the 2019 Arizona Diamondbacks.

The D-backs are clearly deliberate in terms of when they choose to run, but the actual data on when they run is a bit noisy. They’ve feasted on division opponents, converting 29 of 31 stolen-base attempts. But they’ve also gone 21-of-25 against non-division catchers, so it’s hard to argue that familiarity with the opponent is their secret sauce.

As far as specific situations go, the D-Backs love running early in the game. They’ve attempted 10 steals in the first inning this year, and 37 total in innings 1-5, with just 19 more coming in the second half of games and extra innings. At first, that struck me as a bit curious. After all, if a game is close late, advancing one base could be that much more crucial to scoring an important run. But these are the 2019 Arizona Diamondbacks, and it stands to reason that a careful team would consider a baserunner too valuable late in a game to risk losing.

They’re more consistent when it comes to particular counts they run in, attempting 20 steals in even counts, 19 in hitter-friendly counts, and 17 in pitcher-friendly counts. They have yet to be caught when running with the pitcher ahead in the count, probably because that situation yields a higher percentage of non-fastball offerings.

While the Diamondbacks’ efficiency on the bases this season has been laudable, it does prompt a question: Why not run more? If the team has tapped into some kind of breakthrough in terms of how to steal with this kind of success rate, and there are intelligent speedsters up and down the lineup, why not attempt to get even more out of that? It’s a reasonable thing to ask, and it seems as though Arizona may be exploring it as well. In the 17 games they’ve played since June 19, they’ve attempted 14 steals. That’s just over four steal attempts every five games, after attempting roughly one steal for every two games played up until that point. All 14 of those attempts have been successful. After half a season of swiping bags at a historic rate, it seems like Arizona has begun to lean even further into their advantage.

Overall, the Diamondbacks have an active streak of 15 consecutive successful steals, after holding a separate streak of 17 straight earlier this season. Four more without being caught would place them at 90% over 60 attempts, and that is a bigger deal than it may seem.

Despite the recent increase in analytically minded players and personnel over the past 10-15 years, league-wide stolen-base percentages have remained mostly stagnant. In 2009, the league’s success rate on stolen base attempts was 72.4%. In 2019? Again, 72.4%. A 90% stolen-base percentage today, in fact, would be an even bigger departure from league average (17.6%) than the Big Red Machine’s 80% success rate was in 1975 (15.2%).

When the 80% stolen-base percentage threshold was reached for the first time, it was an unprecedented mark of baserunning efficiency. More than 40 years later, the D-backs have a chance to do the same thing, and that could serve as a significant indicator for where the game is going. Last season featured the lowest stolen-base total in a non-strike season since 1973, and that number is set to drop once again this year. Teams are running less than they have in decades and placing more of a premium than ever on getting the most out of every event that happens on the field.

The D-backs don’t need to hit 90% to become the most efficient base-stealing team in history, and they don’t even need to beat the Phillies’ mark to be historically significant. But as they wait to begin the second half of their season, they’re on the cusp of doing something we’ve never seen before. For years, wiser approaches to stolen bases have done relatively little to shift the possibilities of what teams can accomplish with them. The 2019 Arizona Diamondbacks are raising that ceiling.