Research room: The true value of Marte’s ability to steal bases

Welcome to Pittsburgh Pirates Research Room, a semi-regular feature in which we break out the chalkboard, the protractors and all sorts of other tools to go in-depth on ideas, practices and more abstract thoughts that surround the Pirates.

Starling Marte rejoining the Pittsburgh Pirates is arguably the best upgrade any major league team will get this season prior to the trade deadline.

Marte is an obvious fielding upgrade, with good speed, a good arm, and a knowledge of fielding the outfield not shared by the likes of John Jaso or Adam Frazier. And that is not a knock on his replacements, but rather to say that Marte is just that good.

Furthermore, the fact that Jaso and Frazier are now bench players means that the bench gets an upgrade over the likes of Phil Gosselin for example. Marte’s bat is also a plus, with a career .788 OPS versus Frazier (.727) and Jaso (.763).

Those stats are all well and good, but a true dimension of the game that Marte uniquely brings to the team is that of his speed on the bases.

The best burglar in the bunch

From Marte’s first full season with the Pittsburgh Pirates in 2013 to the end of last year, he alone accounted for nearly one-third of all Pirates stolen bases. In 2016, Marte’s 47 swiped bags made up 43% of the team’s swipes.

It’s also clear that the Pirates are unable to produce as much speed on the bases without him; 99 games into the 2017 season, subtracting out Marte’s 5 SB, the Pirates have only stolen 41 bases, putting them on pace for just 67 this year.

To put that into perspective, that would be the lowest season total since the team’s 95 loss season nearly a decade ago in 2008. Obviously Marte poses a threat on the base paths unmatched by anyone else on the Pirates roster. If Marte produces a similar rate of base stealing as last year that would put him on track for 24 Stolen Bases this year, which would put the Pirates projected total at 91, or 7th highest team total since 2000.

To steal or not to steal: a cost-benefit analysis

In order to quantify the value that Marte brings to the Pittsburgh Pirates in terms of base stealing, we first have to understand what the costs and benefits of such thievery are.

While base stealing is a skill that can certainly put a team in a better position to win, it can also cost a team wins if a player is caught stealing and yields key outs. Teams can “run themselves” out of a win by attempting to steal and getting caught, thus the benefits of a stolen base can be offset by the costs of being caught stealing. We can quantify these costs and benefits by creating a statistical model of runs using hits, walks and base stealing. Mathematically speaking, we can estimate runs in a function like this;

Where the different X’s represent the different coefficients, or linear weights, of the variables they are multiplied by. In this analysis, the only terms we really care about are the X₈ and X₉ terms for SB and CS respectively. Using all 30 teams individual season data from 2010-2016, here’s what our statistical model looks like;

Pay attention to these numbers

Highlighted in the gold box are the coefficients X₈ and X₉ for SB and CS, meaning that a Stolen Base is worth .250 runs and a Caught Stealing costs .357 runs. Using this information we can then set up a formula known as Stolen Base Runs, or SBR for short, which estimates the value that a player or a team generated in terms of additional runs scored, from just base stealing. This formula looks like this;

To find the break-even point, or the point where a team is neither harming nor helping their offense by stealing bases, we just have to set this formula equal to zero and solve:

In other words – a player would need to steal 1.429 more bases than you get caught stealing or steal at about 60 percent rate (it’s actually 58.8 percent) to break even in runs in the modern era.

You may sometimes hear that teams need to steal at 70 percent or higher rate in order to make base stealing worth it. This could be due to the fact that a clip of around 70 percent will net a team 10 additional runs on average over the course of a 162 game season.

An additional 10 runs, all else being equal, is worth about 1 additional win per season, and that’s why the 70 percent figure is so heavily relied upon.

Furthermore, there are other unseen costs in addition to a CS, like an injury that can happen when trying to slide in under a tag. Take the example of Mike Trout from earlier this season; Trout injured his thumb stealing second. The quarter of a run generated by Trout stealing that base were by no means worth the cost of the additional wins Trout would have generated over the 39 games he missed due to injury, so, again, the 70 percent figure is used to cover those “unseen” costs like injury etc.

So, time to gauge Marte’s base stealing value

Getting back to Marte and the Pittsburgh Pirates, we can now find the value of Marte’s base stealing abilities for this season.

As previously stated the Pirates are on pace for 67 SBs without Marte, they are also on pace for 39 CS. Using his 2016 numbers projected onto this 82 game season for Marte, he should generate about 24 SB and 6 CS. Plugging these numbers into the SBR formula we get;

Pirates without Marte:

Marte:

Pirates with Marte:

While I think it was obvious to most fans that Marte was going to be a plus on the base paths, I certainly was not expecting it to be on this scale.

Marte is projected to be worth one full run more than the rest of the Pittsburgh Pirates combined in terms of offense generated from swiped bags, all this in just half the amount of playing time. Furthermore, just looking at Stolen Base Rates, without Marte the Pirates are projected to steal bases at 63 percent, which is a little too close to the break-even point for comfort.

However, with just a half season of Marte, the Pittsburgh Pirates are projected to steal at 67 percent, much closer to the accepted 70 perent target. In terms of SBR, in 2016 Marte was worth about 7.5 SBR, in other words about 75 percent of a win, on the base paths alone, which makes his suspension that much harder to take.

[perfectpullquote align=”full” cite=”” link=”” color=”” class=”” size=””]From Marte’s first full season with the Pittsburgh Pirates in 2013 to the end of last year, he alone accounted for nearly one-third of all Pirates stolen bases[/perfectpullquote]

Marte’s presence on the team is an obvious upgrade. His base stealing alone is estimated to be worth about 0.4 additional wins over the course of the remainder of the 2017 campaign, relative to where the team was without him.

Setting aside his bat and glove, and the upgrades that they bring to the team, Marte’s speed on the bases alone is more than doubles the value of what the Pittsburgh Pirates would have produced without him.

This just serves to highlight how quickly that the value of a good base stealer can add to a team’s win column. It also underscores the hole that was created by Marte’s suspension, and the improved possibility for this team to win more games in the second half of the season with him in the lineup.