Common Mistakes When Reading Baseball Stats

• Judging a pitcher by ERA alone. ERA mixes the pitcher with his defense, his park and sequencing luck. Strikeouts, walks and quality of contact allowed (xwOBA) are more stable and predict future runs better.
• Trusting small samples. A hitter's 10-for-20 against a pitcher tells you almost nothing; see Early-season stats and small samples.
• Ignoring the park. A 4.20 ERA at Coors Field is excellent; the same number at T-Mobile Park is poor. See park factors.
• Forgetting the bullpen. Starters pitch about five innings now; the relievers behind them decide a lot of games.
• Reading win-loss records for pitchers. Wins depend on run support and bullpens.
• Mixing eras. League scoring changed a lot between 2019 and 2026; compare players with their own season's league average.
• Treating a probability as a promise. A 65% projection loses about one time in three. See what a win probability means.

BullpenEdge's pitcher and team pages are built around these lessons: rates instead of totals, league-relative numbers, and every projection regressed by how much evidence stands behind it.