OBJECTIVE: To investigate the relationship between training/match-play duration and time-loss groin injury in professional male soccer players, and to determine whether previously identified intrinsic risk factors influenced this relationship. DESIGN: Prospective cohort study. METHODS: A total of 579 professional male soccer players were prospectively followed from July 2013 to June 2015. Time-loss groin injuries and individual training and match-play duration were recorded using standardized surveillance methods. Acute training/ match-play duration and chronic training/match-play duration were considered as interacting variables. Nonlinear Cox regression analysis (modeled using restricted cubic splines), clustered by player identification number, examined the relationship between training/match-play duration and groin injury. Previously identified intrinsic risk factors of previous groin injury and eccentric adduction strength were included in the multivariable regression analysis. RESULTS: There was no clinically meaningful relationship between training/match-play duration and groin injury risk. Team played for had the strongest influence on groin injury risk (relative log hazard ratio -2.28 to 0.97). Groin injury risk was highest when accumulated chronic and acute training duration was also highest, but large confidence intervals indicate considerable uncertainty around this finding. Previous groin injury and eccentric adduction strength were not associated with groin injury risk when training/match-play duration and team were included in the model. CONCLUSION: In professional male soccer players, there was no clinically meaningful relationship between groin injury risk and training/ match-play duration. Team played for either protected against or increased groin injury risk, indicating that team-related factors not measured in this study had greater effect on groin injury risk than training/match-play duration.