Abstract
This study aims to evaluate the effectiveness of z-score and Total Score Athleticism (TSA) in distinguishing between drafted and undrafted NFL players, with a focus on different positional groups. We analyzed NFL Scouting Combine data (2000-2024) using z-score and TSA calculated for both the entire sample and specific positional groups (Skill player, big skill player and linemen), with a final sample of 3,446 players included after filtering. Examine the differences between drafted and undrafted players, as well as the differences among the three positional groups. The classification accuracy was evaluated by ROC analysis and binary logistic regression. Significant differences were observed in z-scores (P < 0.001) and TSA (P < 0.001) between drafted and undrafted players under the two calculation methods across all positions, with drafted players generally outperforming undrafted ones. ROC analysis indicated that all z-scores on NFL SC demonstrate good performance (AUC > 0.6, P < 0.001). Z-score for the 40-yard dash provided the highest AUC (0.637-0.719), while the bench press lowest (0.556-0.631). Position-specific z-score and TSA calculations showed better discriminatory performance compared to the calculation based on the overall sample. This study confirms that both z-scores and TSA are effective in differentiating drafted from undrafted players, with position-specific calculations offering enhanced discriminatory power. The results underscore the importance of tailoring athletic assessments to specific positional needs to improve talent identification. Coaches can understand how z-scores and TSA can be used on National Football League Scouting Combine, and these metrics perform across various positions.