Contemporary models of athlete development (e.g., Development Model of Sport Participation) suggest attainment benefits from early age multi-sport 'sampling' behaviour before progressive transition into 'invested' single-sport involvement in teenage years relative to intensive early-age specialisation. However, specific examinations of these development patterns across a number of team sports and cultural contexts remains limited. This study involved a large sample of professional Australian Rugby League (RL) players (N = 224) who progressed along the RL system pathways. Their development was examined using the National Rugby League Athlete Development Questionnaire (NRLADQ). Two contrasting athlete development trajectories were identified based upon initial entry into formal age-group representative teams ("Early": U16, U18; "Later": U20+) and developmental participation patterns were compared. Between-Within Analyses of Variance (BW-ANOVA)'s identified interaction effects as the 'Later'group reported lower volumes of deliberate practice from 10-20 years, RL-game involvement from 10-20 years, deliberate play from 5-12 years, and a later reduction in other sporting involvement. Group differences in RL-related deliberate practice and play were supported by qualitative descriptions of training at age-categories. Findings identified that RL professional senior elite success can be attained via early intensified specialised investment and accelerated youth success as well as a rather decelerated, less cost-intensive participation pattern.