What is Run Prevention? Definition, Formula, and Example
Run prevention is the comprehensive art and science of limiting opposing teams from scoring, encompassing pitching, fielding, and defensive positioning.
What is Run Prevention in Baseball?
Run prevention is the comprehensive art and science of limiting opposing teams from scoring. It encompasses every defensive aspect of the game: pitching, fielding, pitch framing, and defensive positioning. While traditional baseball divided defense into pitching (handled by the mound) and fielding (handled by the gloves), modern front offices view run prevention as a single, interconnected ecosystem. A team's ability to prevent runs dictates its defensive efficiency, which is just as critical to winning as scoring runs.
How Run Prevention is Measured
Run prevention is not a single statistic but a holistic evaluation measured through several advanced metrics. The foundational formula for expected team wins relies on runs scored versus runs allowed (the Pythagorean Winning Percentage), making run prevention half of the winning equation.
To quantify run prevention, analysts use metrics like Fielding Independent Pitching (FIP) to isolate a pitcher's true contribution, Defensive Runs Saved (DRS) and Outs Above Average (OAA) to measure fielding value, and Framing Runs to evaluate catchers. The aggregate of these metrics, adjusted for park factors, provides a total Run Prevention score. Specifically, a team's total defensive value can be summarized by combining a pitcher's FIP with the fielders' cumulative DRS or OAA.
Worked Example
The 2022 Houston Astros provide a masterclass in run prevention. During the regular season, they allowed just 518 runs, the fewest in the American League. Their pitching staff posted a collective 2.90 FIP, led by Justin Verlander's 2.83 FIP and 1.75 ERA. However, their run prevention was bolstered by elite fielding; the Astros infield posted a combined +31 Outs Above Average (OAA), with Jeremy Peñas accounting for +10 OAA at shortstop alone. By combining Verlander's strike-throwing with Peñas's web-gem defense, the Astros turned high-percentage batted balls into outs, suppressing opponent run expectancy by an estimated 45 runs over the season compared to an average defense.
Why Run Prevention Matters
Run prevention drives nearly every modern front-office decision. Teams draft and develop pitchers based on Stuff+ and FIP, knowing that strikeouts (which require no fielding) are the purest form of run prevention. Positional acquisitions are heavily influenced by OAA and DRS, shifting the market toward elite glovemen like Andrelton Simmons or Bobby Witt Jr. For fantasy baseball and DFS players, understanding a team's run prevention capabilities is vital for evaluating pitchers; a mediocre pitcher on a team with elite OAA and framing will outperform his individual peripherals. In Legends Deck, run prevention metrics directly dictate defensive card ratings, influencing how often your virtual cards convert batted balls into outs.
Limitations and Common Misconceptions
A common misconception is that run prevention is entirely dependent on the pitcher. While the pitcher initiates the play, a poor defense can drastically inflate a pitcher's ERA without reflecting a drop in their actual stuff. Conversely, a pitcher with a high ERA but low FIP is often suffering from bad fielding, not bad pitching. Run prevention metrics can also struggle to quantify the exact value of defensive positioning (the shift) and the cumulative fatigue of a bullpen over a 162-game season. Additionally, DRS and OAA can vary year-to-year due to small sample sizes on specific batted ball types.
Related Terms
In Legends Deck: Run prevention algorithms power the defensive attributes on player cards. A pitcher's card will perform better in simulations when backed by high-OAA fielders, simulating the real-world synergy of elite pitching and elite defense.