What is Caught Stealing Probability? Definition, Formula, and Example
Caught Stealing Probability (CS Prob) is a Statcast metric that calculates the likelihood of a baserunner being thrown out attempting to steal a base, expressed as a percentage from 0% to 100%.
What is Caught Stealing Probability?
Caught Stealing Probability (CS Prob) is a Statcast metric that calculates the likelihood of a baserunner being thrown out attempting to steal a base, expressed as a percentage from 0% to 100%. Introduced alongside the sprint speed and pop time metrics, CS Prob isolates the exact moment the pitch crosses home plate and evaluates the race between the runner and the catcher's throw. It removes the binary "safe or out" result and replaces it with a granular, data-driven probability that accounts for the runner's speed, the catcher's pop time, the pitcher's delivery time to the plate, and the exact lead the runner achieved.
How it is Calculated / Measured
Statcast calculates CS Prob by analyzing the physical inputs of a stolen base attempt at the moment the pitch reaches the front of home plate. The primary variables include:
1. Runner's Lead Distance: The exact distance from the runner's center of mass to the center of the base he is occupying (measured in feet).
2. Runner's Sprint Speed: The baserunner's established maximum sprint speed (measured in feet per second).
3. Pitcher's Time to Plate: The time elapsed from the pitcher's first movement to the moment the pitch crosses the front of home plate.
4. Catcher's Pop Time: The time it takes for the catcher to receive the pitch, transfer the ball, and release his throw to the specific base.
The model evaluates the remaining distance the runner must cover to reach the next base, subtracts the distance the runner covers during the catcher's pop time and throw transit time, and outputs a percentage. A 90% CS Prob means the defense executed the play perfectly and the runner's jump was poor enough that the expected outcome is an out nine times out of ten.
Worked Example
During the 2023 season, catcher J.T. Realmuto threw out a runner attempting to steal second base. The Statcast data for the play revealed:
- Runner's Lead: 18.5 feet
- Runner's Sprint Speed: 27.5 ft/sec
- Pitcher's Time to Plate: 1.45 seconds
- Realmuto's Pop Time: 1.92 seconds
- Throw Transit Time: 1.10 seconds
With a total defensive time of 3.02 seconds from pitch release to the ball arriving at second base, the runner had to cover approximately 63.5 feet (90 feet between bases minus the 18.5-foot lead, plus overshoot distance). The CS Prob model calculated the out probability at 82% for this specific attempt. Realmuto's elite pop time and the pitcher's quick delivery combined to heavily outweigh the runner's above-average speed and aggressive lead.
Why it Matters
CS Prob matters because it strips luck and poor execution out of stolen base evaluation. For front offices, it identifies which catchers possess true elite throwing ability versus those who benefit from facing slow runners or poor pitcher delivery times. It also evaluates baserunners independently of the catcher; a runner can be thrown out but still register an 85% safe probability, proving he took an excellent jump and simply got beat by a perfect throw. For fantasy baseball and DFS players, tracking CS Prob helps predict whether a high-volume base stealer will maintain his success rate or regress due to poor jumps.
Limitations / Common Misconceptions
CS Prob does not account for the type of pitch thrown. A 95 mph fastball at the top of the zone is easier for a catcher to transfer and throw than a 85 mph splitter in the dirt. Catcher framing and blocking duties can artificially inflate or depress a catcher's CS Prob. Furthermore, the metric assumes perfect throw accuracy from the catcher and perfect catching of the ball by the middle infielder. It measures the physical race, not the execution of the tag. It is often confused with Caught Stealing Percentage (CS%), which simply divides caught stealings by total attempts without factoring in the quality of the runner or the lead.
Related Terms
In Legends Deck
In Legends Deck, CS Prob informs the Baserunning and Fielding attributes on player cards. A high CS Prob against elite runners boosts a catcher's defensive rating, directly impacting the simulation's odds of erasing a stolen base attempt during a simulated game. When you deploy a catcher with elite CS Prob numbers, the game engine applies a penalty to the opposing manager's steal attempts, protecting your lead.