Skipper: Manage a Game With the Numbers

What you are learning while you play

Run expectancy. Every base and out situation is worth a number of runs on average. Every play moves that number. Outs are expensive. A bunt usually trades a base for an out and loses value. The table in the game shows it live.

Real MLB run expectancy, 2010 to 2015 (The Book)
Runners      0 out   1 out   2 out
Empty        0.48    0.25    0.10
1st          0.86    0.51    0.22
2nd          1.10    0.66    0.32
1st, 2nd     1.44    0.88    0.43
3rd          1.35    0.95    0.35
1st, 3rd     1.78    1.13    0.48
2nd, 3rd     1.96    1.38    0.58
Loaded       2.29    1.54    0.75

The count. Every pitch changes the hitter's odds. After 0-1, big leaguers are about 16 percent worse than average. After 2-0, about 35 percent better. After 0-2, about 37 percent worse. That is why "strike one" is the most important pitch. The game's count bar shows the real MLB number after every pitch, and the engine is tuned so its counts land close to those numbers.
```
MLB wOBA after each count (FanGraphs, 2020)
.320 is average
        0 strikes  1 strike  2 strikes
0 balls   .320      .270      .203
1 ball    .363      .303      .228
2 balls   .434      .361      .273
3 balls   .544      .476      .377
```
Break-even math. A stolen base is worth trying only if the runner's chance beats the break-even rate for that situation, usually around 70 percent. The game does the division for you and shows the work.
Physics decides hits. Each ball in play gets an exit velocity and launch angle, then flies with drag and spin. Fielders race it. Nothing is a dice roll that says "single."
Expected value, not outcomes. A good call can still fail. A bad call can still work. The report at the end grades your decisions by the math at the time, not by how the ball bounced.
Pitch counts and fatigue. Pitchers lose control and velocity as they tire. Youth levels have a hard pitch cap. Managing the staff is part of the job.
The 20 to 80 scale. Scouts grade players this way. 50 is average, 80 is the best you will ever see, 20 is the lowest. Reading a scout report is reading a number line.

Where the ideas come from

Earl Weaver managed the Orioles from 1968 to 1982, and again in 1985 and 1986. In Weaver on Strategy (1984) he laid out his laws, including "The easiest way around the bases is with one swing of the bat," "Your most precious possessions on offense are your twenty-seven outs," and "If you play for one run, that's all you'll get." Run expectancy math, worked out decades later in The Book, mostly agrees with him. The other dugout in this game manages the Weaver way: no sacrifice bunts, steals only with fast runners.

The 1987 computer game that carried his name was one of the first to put a manager's thinking and real ballpark dimensions into software, and let you ask the manager for advice. That is where "Ask the numbers" comes from.

For coaches and parents

Play it next to them. The learning is in the pause before the call. Good questions: Why is the bunt a negative number here? What would make the steal worth it? Why did the fly out score a run?

Do not use this to grade real players or real decisions. The rosters are invented, the physics is simplified, and youth games have far more randomness than any model shows. Use it to build the habit of thinking in expected value, then go play catch.

Guidelines & sources this game follows

Tango, T., Lichtman, M., and Dolphin, A. (2007). The Book: Playing the Percentages in Baseball. Run expectancy by base and out state, sacrifice bunt and stolen base break-even analysis. The real MLB table is printed above. The in-game table is built from this game's own engine, 1,500 simulated innings from each situation at each level, so that the advice matches the game you are playing.
Clemens, B. (2020). The Count Is King (Even After Accounting for Batter Skill). FanGraphs. MLB wOBA after each ball-strike count, used for the count bar and to tune the engine. blogs.fangraphs.com
Associated Press with Sportradar (2025). MLB hitters swing at 32.1 percent of first pitches and hit .338 when they put the first pitch in play. AP report
Weaver, E., with Pluto, T. (1984). Weaver on Strategy. Weaver's laws of managing, quoted above.
Nathan, A. M. The Physics of Baseball (University of Illinois). Drag, lift, and air density. baseball.physics.illinois.edu
MLB Statcast glossary. Exit velocity, launch angle, sweet spot. mlb.com/glossary/statcast
Little League Baseball Regular Season Pitching Rules. Pitch count limits by age (85 per day for ages 11 to 12, 95 for 13 to 16). littleleague.org/playing-rules/pitch-count
Lewis, M. (2003). Moneyball. Outs are the scarce resource. Measure what happens.
Lindbergh, B., and Sawchik, T. (2019). The MVP Machine. How exit velocity and launch angle changed player development.

Note on certainty: this is a simplified model. Pitch outcomes, baserunning, errors, and fatigue are rough estimates tuned to look like real games, not measured from youth data. The run expectancy numbers come from this engine, not from youth game data. The count numbers are MLB; youth hitters see more balls and struggle more with two strikes, so the gaps are probably bigger at young ages, but we have no youth data to prove it. "Ask the numbers" runs a few hundred simulations of this game's own engine, so it tells you what the model thinks, not what a real game would do. Treat every number as a lesson in thinking, not a fact about your team.

Want to feel the physics by hand first? Try Launch Lab.