Mary Earps vs Alyssa Naeher Shot Stopping Calculator

The Mary Earps vs Alyssa Naeher Shot Stopping Calculator compares their goalkeeper shot-stopping metrics from recent matches and predicts save probability under various scenarios.

What Is a Mary Earps vs Alyssa Naeher Shot Stopping Calculator?

This calculator is a sport analytics tool that estimates and compares the shot-stopping performance of Mary Earps and Alyssa Naeher. Shot stopping is the skill of turning dangerous shots into saves. The tool centers on post-shot expected goals (PSxG), which rates the likelihood a shot on target becomes a goal based on its placement, speed, and trajectory.

Unlike basic save percentage, PSxG accounts for shot difficulty. A curling top-corner strike carries higher PSxG than a slow, central shot. By combining PSxG with goals conceded and shots on target faced, the calculator estimates goals prevented and efficiency metrics adjusted for sample size and play time.

It also offers normalization per 90 minutes and can separate penalties from open play. This ensures fair comparisons even if one keeper faces more minutes, different shot profiles, or has large penalty volumes that can skew save rates.

The Mechanics Behind Mary Earps vs Alyssa Naeher Shot Stopping

The calculator processes your inputs into comparable metrics. It first evaluates how hard the shots were, then how many goals were actually conceded. It adjusts for playing time and can benchmark against league averages to gauge above-average performance.

• Quality-of-shot modeling: Uses PSxG-on-target to quantify chance of a goal after the ball is struck and placed.
• Volume adjustment: Considers shots on target faced, preventing small-sample overreactions.
• Outcome check: Compares expected goals conceded (PSxG) with actual goals against to estimate goals prevented.
• Time normalization: Scales key figures per 90 minutes for fair comparisons across different minutes played.
• Context filter: Optionally isolates penalties, set pieces, or open play to reduce noise from special situations.

The result is a head-to-head display of who saved more versus expectation, who faced tougher shots, and who maintained consistency across minutes. It shows efficiency, not just totals, so a keeper with fewer matches can still be evaluated fairly.

Equations Used by the Mary Earps vs Alyssa Naeher Shot Stopping Calculator

The calculator relies on transparent equations. Below are the core formulas used to compare each goalkeeper, then the difference between them. Definitions appear on first mention to keep terms clear.

• Save Percentage (SV%): SV% = Saves / Shots on Target Faced.
• Expected Save Percentage (xSV%): xSV% = 1 − (PSxG / Shots on Target Faced).
• Goals Prevented (GP): GP = PSxG − Goals Against. Positive GP means better-than-expected shot stopping.
• Goals Saved Above Average (GSAA): GSAA = Saves − (Shots on Target Faced × League-Average SV%).
• PSxG per Shot (PSxG/SoT): PSxG/SoT = PSxG / Shots on Target Faced. Higher values indicate tougher shots faced.
• Per-90 Scaling: Metric per 90 = (Metric ÷ Minutes Played) × 90.

These equations isolate shot-stopping from team effects as much as possible. You can also compute separate GP or SV% excluding penalties, then compare the open-play figures for a different angle on performance.

What You Need to Use the Mary Earps vs Alyssa Naeher Shot Stopping Calculator

Collect a few match-level or season-level inputs for each goalkeeper. Most are available on advanced stat sites or official league reports. Using consistent sources for both players prevents hidden bias in the comparison.

• Shots on Target Faced (SoTF): Count of shots that required a save or became a goal.
• Goals Against (GA): Total goals conceded, optionally split into open play and penalties.
• Post-Shot Expected Goals (PSxG): Sum of goal probabilities for all shots on target faced.
• Minutes Played: Total minutes in goal to scale metrics per 90.
• League-Average Save Percentage (LgSV%): Baseline save rate for normalization (same league and season).
• Penalty Details (optional): Penalties faced and conceded, for exclusion or separate analysis.

Typical ranges: SoTF can vary from 30 to 200+ depending on sample size. PSxG will roughly track SoTF and average shot quality. Edge cases include very small samples, extremely high PSxG per shot due to rare screamers, or a cluster of penalties that inflate GA. The calculator flags small-sample outputs as less stable.

Step-by-Step: Use the Mary Earps vs Alyssa Naeher Shot Stopping Calculator

Here’s a concise overview before we dive into the key points:

1. Choose your sample window (season, tournament, or custom date range).
2. Enter Shots on Target Faced, Goals Against, and Minutes Played for each goalkeeper.
3. Enter PSxG totals for each goalkeeper for the same window.
4. Input the League-Average Save Percentage for the same league and season.
5. Decide whether to exclude penalties, then toggle the penalty filter if needed.
6. Review computed SV%, xSV%, Goals Prevented, GSAA, and per-90 versions.

These points provide quick orientation—use them alongside the full explanations in this page.

Example Scenarios

Scenario A: Over 1,800 minutes, assume Earps faces 80 shots on target with PSxG = 24.0 and concedes 18 goals. Naeher faces 75 shots on target with PSxG = 22.5 and concedes 20 goals. Earps GP = 24.0 − 18 = +6.0; Naeher GP = 22.5 − 20 = +2.5. Per 90, Earps GP/90 = (6.0 ÷ 1,800) × 90 = 0.30; Naeher GP/90 ≈ (2.5 ÷ 1,800) × 90 ≈ 0.125. What this means: Earps outperforms expectation more often, with a larger positive impact per 90.

Scenario B (penalties excluded): Over 900 minutes, Earps’ open-play PSxG = 10.5 with 8 goals conceded; Naeher’s open-play PSxG = 9.2 with 6 goals conceded. Earps open-play GP = 10.5 − 8 = +2.5; Naeher open-play GP = 9.2 − 6 = +3.2. Both face similar shot volumes, but Naeher’s GP/SoTF is slightly higher, suggesting marginally better performance against the particular shot mix. What this means: With penalties removed, Naeher edges the comparison in this short sample, but stability is limited.

Assumptions, Caveats & Edge Cases

Shot-stopping models rely on accurate event and tracking data. If PSxG estimates disagree across providers, results will differ. Small samples and extreme shot profiles can distort save percentage and goals prevented, especially when several penalties cluster in a short span.

• Provider variance: PSxG models differ by definitions, modeling inputs, and calibration methods.
• Penalty treatment: Penalties carry high expected value; mix them carefully or analyze separately.
• Defense context: Teammate pressure and shot blocking influence shot quality before the strike.
• Game state effects: Leading or trailing can change shot quality faced and keeper behavior.
• Regression to the mean: Exceptional runs often moderate as sample size grows.

Use the calculator as a decision aid, not a standalone verdict. Cross-check with video and scouting notes to understand technique, positioning, and command of area that metrics may not fully capture.

Units & Conversions

While the core outputs are unitless rates or “goals,” inputs like shot speed, distance, and time can affect PSxG in source models. If you audit or add custom inputs, consistent units are essential. Use the conversions below to align data from different feeds.

Apply these conversions before entering any custom speed, angle, or distance values into a model that feeds PSxG. Mixing units can silently skew expected values and mislead comparisons.

Common Issues & Fixes

Most problems arise from inconsistent data windows, mixed competitions, or model differences. Another common pitfall is including penalty data in one keeper’s totals but excluding it in the other’s. That creates biased comparisons.

• Mismatch in minutes or competitions: Align the same leagues, tournaments, and dates for both players.
• Different PSxG providers: Stick to one provider per comparison or note the change.
• Penalty mixing: Either include or exclude penalties for both keepers consistently.
• Small samples: Flag and interpret with caution; rely on per-90 and confidence notes.

If the numbers seem off, re-check inputs for rounding or entry errors. Make sure PSxG and shots on target refer to the same set of matches and time on pitch.

FAQ about Mary Earps vs Alyssa Naeher Shot Stopping Calculator

How is post-shot expected goals (PSxG) different from xG?

xG estimates goal probability at the moment of the shot based on location and context. PSxG uses the shot’s actual placement and trajectory to refine the probability after contact. PSxG is better for measuring goalkeeper performance.

Should I include penalties in the comparison?

Penalties have very high expected value and can dominate small samples. Many analysts present two views: one including penalties and one excluding them. The calculator supports both.

Why compute per-90 metrics?

Per-90 scaling controls for different minutes played. It allows fair comparisons when one goalkeeper has fewer matches or is rotated across competitions.

What does a positive Goals Prevented (GP) mean?

Positive GP means the goalkeeper conceded fewer goals than expected given the quality of shots on target faced. It indicates above-expectation shot stopping over that sample.

Key Terms in Mary Earps vs Alyssa Naeher Shot Stopping

Shots on Target Faced (SoTF)

The number of opponent shots that would score without a save or that do score. Blocks off target do not count.

Goals Against (GA)

Total goals conceded by the goalkeeper’s team while the goalkeeper is on the field. Own goals are typically included by competition rules, but may be excluded from PSxG comparisons.

Post-Shot Expected Goals (PSxG)

A model-based sum of goal probabilities for shots on target, informed by shot placement, height, speed, and trajectory. Higher PSxG implies tougher saves on average.

Save Percentage (SV%)

The share of shots on target saved: saves divided by shots on target faced. It is simple but does not account for shot difficulty.

Goals Prevented (GP)

The difference between PSxG and goals conceded. Positive values indicate better-than-expected shot stopping; negative values indicate worse-than-expected.

Goals Saved Above Average (GSAA)

Saves above a league-average baseline: saves minus the product of shots on target and league-average save percentage. Useful for cross-team context.

Per 90 Minutes (per 90)

A normalization that expresses a metric for every full 90 minutes of play. It enables fair comparisons across different playing times.

Penalty Exclusion

An option to remove penalties from calculations, reducing variance and highlighting open-play shot stopping.

Sources & Further Reading

Here’s a concise overview before we dive into the key points:

• FBref Glossary: definitions for PSxG, Goals Prevented, and goalkeeper stats — https://fbref.com/en/about/glossary.shtml
• The Analyst by Opta: What is Expected Goals on Target (xGOT)? — https://theanalyst.com/na/2021/08/what-is-expected-goals-on-target-xgot/
• StatsBomb: Expected Goals (xG) explained and modeling context — https://statsbomb.com/articles/soccer/what-is-expected-goals-xg/
• Mary Earps player page with advanced goalkeeping stats — https://fbref.com/en/players/62fb5e96/Mary-Earps
• Alyssa Naeher player page with advanced goalkeeping stats — https://fbref.com/en/players/9d4bbdc0/Alyssa-Naeher
• Wikipedia overview of Expected Goals (xG) for broader background — https://en.wikipedia.org/wiki/Expected_goals

These points provide quick orientation—use them alongside the full explanations in this page.