September 7, 2026
In the peer-reviewed study, "Analysis of Z-Score and total score of athleticism on drafted and undrafted players from the NFL scouting combine", researchers Yifan Zhao, Xiaobin Wei, and Kewei Zhao examine decades of physical combine data to evaluate talent identification in professional football. Published in Scientific Reports, their landmark paper demonstrates how standardizing raw athletic metrics into position-specific Z-scores and aggregating them into a Total Score of Athleticism (TSA) can reliably separate drafted prospects from their undrafted peers. By shifting the focus from noisy, absolute benchmarks to relative positional dominance, their work offers a modern, mathematically rigorous blueprint for identifying true athletic outliers
Every spring, NFL front offices, scouts, and millions of fans tune in to watch draft prospects run, jump, and lift at the NFL Scouting Combine. Historically, evaluation has relied heavily on raw numbers like a 40-yard dash time of 4.4 seconds or 25 repetitions on the bench press. However, evaluating elite athletes based solely on absolute measurements introduces significant noise. A 4.8-second 40-yard dash is a highly draftable, elite measurement for a 300-pound offensive tackle, but it is a franchise-altering failure for a 190-pound wide receiver. To unlock true predictive value, evaluations must shift away from raw numbers and instead ask a more sophisticated question: how much better is a prospect's athleticism compared to their exact positional peers? Standardized Z-scores and the Total Score of Athleticism framework provide the exact mathematical lens needed to isolate this athletic signal.
Standardizing combine performances begins with calculating a Z-score for each athlete in each physical test. This metric is constructed using a straightforward formula where the average score of the population is subtracted from the athlete's individual test result, and the difference is then divided by the population's standard deviation. Mathematically, a Z-score of zero represents an exactly average performance among the peer group. A positive Z-score indicates a performance above average, while a negative score represents a performance below average. Because the score measures standard deviations rather than raw units of time or distance, it allows scouts to compare entirely different physical tests on a single, standardized scale. Rather than struggling to weigh bench press repetitions against sprint times, evaluators can immediately see which test represents a player's greatest relative physical dominance.
A critical flaw in standard combine analysis is evaluating all prospects against a general, undifferentiated historical average. To overcome this, players must be segmented into distinct positional ecosystems, typically defined as skill players, big skill players, and linemen. While skill players include wide receivers and defensive backs who rely heavily on absolute vertical speed, linemen consist of offensive tackles and defensive tackles where absolute physical mass and upper-body leverage are vital. If Z-scores are calculated using the entire combine sample, a massive lineman's speed will be compared to a lightweight receiver's speed, yielding highly misleading negative Z-scores that fail to reflect the lineman's actual physical superiority within their role. Research confirms that position-specific calculations dramatically improve the accuracy of predicting whether a player will be drafted. While a standard Total Score of Athleticism calculated across the entire combine sample yields lower accuracy, calculating these metrics within specific positional groups significantly increases the classification performance.
Athletic ability is multidimensional, which means evaluating prospects on a single test index does not match real-world football demands. The Total Score of Athleticism, or TSA, addresses this by summing the individual Z-scores across all six core combine tests: the 40-yard dash, vertical jump, bench press, broad jump, three-cone drill, and shuttle run. The resulting TSA provides a single, comprehensive quantitative profile of a prospect's general physical performance. The data reveals a massive statistical divide between drafted and undrafted prospects. Across years of historical combine data, drafted players consistently demonstrate significantly superior TSA values compared to their undrafted peers. Drafted players on average maintain a positive TSA, while undrafted players average a deeply negative TSA. This stark contrast proves that relative athletic dominance is heavily prioritized by NFL front offices when making selection decisions.
While overall athletic dominance is important, individual physical tests carry different weight depending on the position group. Across all player positions, the 40-yard dash Z-score remains the strongest individual predictor of selection. Statistical regression shows that for every single-point increase in an athlete's 40-yard dash Z-score, their probability of being drafted increases dramatically, with skill players seeing the highest boost, closely followed by big skill players and linemen. This consistent emphasis highlights how short-distance sprint ability aligns with the high-intensity, repetitive sprint demands of football. In contrast, the bench press serves as a much weaker predictor for skill players, where the required baseline of upper-body strength is minimal. However, as evaluations move into the trenches among linemen and big skill players, the bench press Z-score becomes highly predictive, reflecting the vital importance of upper-body power for physical collisions at the line of scrimmage.
The true practical value of positional Z-scores and the TSA framework is that they allow NFL front offices to draft by anomaly. Instead of using raw combine numbers to check arbitrary boxes, teams can identify outlier athletes who possess a significant athletic edge relative to their specific peer group. Standardizing physical performance helps strength and conditioning coaches pinpoint specific structural weaknesses in draft prospects to set targeted training goals. However, while Z-scores and TSA provide an invaluable signal, they measure physical capacity rather than football skill. Complete draft evaluation still requires integrating these standardized athletic baselines with collegiate performance, training background, and on-field technical capabilities to make the most informed investments on draft day.
Article Reference
Zhao, Y., Wei, X., & Zhao, K. (2025). Analysis of z-score and total score of athleticism on drafted and undrafted players from the NFL scouting combine. Scientific Reports, 15, Article 21742
