Slow Runners, Smart Runners: How to Read MLB's Advanced Baserunning Metrics

Here's the thing most box scores never tell you: a player can be one of the most valuable baserunners in baseball without being fast at all. Statcast's Baserunning Run Value is a composite number, and once you pull it apart, you can see whether a runner earns his value with raw speed, sharp decision-making, or both. The 2023–25 New York Mets are the proof — a team near the bottom of the league in sprint speed that still stole bases at a rate nobody matched.

Beyond the Box Score: Understanding Advanced Baserunning Metrics

Stolen base counts lie to you. A runner who swipes 30 bags but gets thrown out 15 times might be helping his team less than a runner who goes 18-for-19. That's the whole reason advanced baserunning metrics exist: they measure runs created or cost, not just attempts. MLB's Statcast system, published on Baseball Savant, evaluates baserunning by generating an estimated success probability for each opportunity, using inputs like runner speed, the outfielder's throwing arm, the runner's position on the basepaths, and the outfielder's distance from the ball and the bases. The runner's actual outcome is then compared against that estimate. In other words, the metrics ask a simple question: did this runner do more than an average runner would have in the same spot?

Baserunning Run Value: The Comprehensive Score

Baserunning Run Value is the headline number, and per Statcast's own definition, it combines both categories of baserunning — stolen bases and extra bases taken — into one overall value figure. Think of it as a runner's total run contribution from everything he does once he reaches base, expressed in runs above or below what an average runner would produce. Because it's built from estimated success probabilities for each opportunity, it rewards runners who succeed in situations where success was unlikely and dings runners who fail in situations where they should have made it. It's a composite, which makes it useful for ranking but opaque on its own — a high number doesn't tell you why a runner is good. That's what the components are for.

Extra Bases Taken: Rewarding Aggression and Opportunity

Extra Bases Taken Run Value isolates the non-steal side of baserunning: going first-to-third on a single, tagging up, stretching a hit. Statcast describes it as a metric that evaluates baserunners (and outfielders, in reverse) in taking or preventing extra bases. The mechanics matter here. For each opportunity, the system estimates a success probability from runner speed, the outfielder's arm, runner position, and outfielder positioning, then compares the player's actual results against that estimated rate — accounting for bases taken, chances taken, and chances passed up. Crucially, this excludes stolen base attempts entirely. So a runner can be graded on his judgment in traffic: did he take the base when the numbers said go, and did he hold when the numbers said stay?

Deconstructing Baserunning Value: Speed vs. Smarts

Here's the framework I use. Baserunning Run Value is the composite; its two components — extra bases and stolen bases — draw on two distinct underlying skills: raw speed and decision-making. The table below decomposes the metric and shows how the Mets case fits each layer.

Breaking down baserunning value into components and skills
Layer	What it measures	Underlying skill
Baserunning Run Value	Total runs above average from all baserunning actions, combining stolen bases and extra bases taken (Statcast)	Composite of both skills below
Extra Bases Taken Run Value	Runs created taking additional bases beyond what an average runner would in similar situations; excludes steal attempts	Speed plus situational judgment on hits and tags
Stolen Base Success Rate	Share of steal attempts that succeed; the Mets led MLB at 85.9% over three seasons	Decision-making, leads, and jumps — not just speed
Sprint Speed (context)	Raw footspeed; the Mets ranked 29th, rising only to 25th when weighted by steal attempts	Pure athleticism

The reasoning path is straightforward. Statcast defines the composite as stolen bases plus extra bases. Each component is graded against situation-specific success probabilities, so a runner's value reflects choices as much as tools. The Mets test the framework: bottom-third speed, below-average extra-base success, elite steal success — and still a top-10 baserunning team. That tells you the composite is capturing judgment, not just wheels.