Based on hypotheses that athlete development can be variable and non-linear across a longitudinal period, and that 'relatively later maturing players' can reduce or negate developmental differences in later adolescence, this study examined a methodological issue concerning how best to assess anthropometric and fitness change relative to a broader population (i.e., 'across age categories' or 'per year'), and changes in case rugby league players (i.e., ages 13-15) across a 2 year period relative

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... o an age and skill matched population (N = 1,172). Findings identified that a 'per year' method generated less deviated z scores across variables, suggesting less substantial change in case players relative to the population. When applied to additional players, z-score and radar graphs still showed developmental variability and longitudinal change, even within a relatively homogenous sample. The possibility of a 'later maturing player' rapidly reducing developmental differences within a two year period was identified. These findings affirm the potential for highly variable and changing trajectories between adolescent athletes, particular for those of differing maturation status. Practical implications point toward advocating a long-term inclusive tracking approach, the avoidance of (de)selection, and the reduction of a performance emphasis at adolescent stages of sport development systems.