The purpose of this study was to analyze the informational constraints that influence the dynamics of 1v1 situations in football. Specifically, we analyzed the contribution of interpersonal distance and relative velocity to explain phase transitions that occurred between stable and unstable coordinative states in 1v1 in football. Participants were six, U13 level football players (Mean age: 11.8±0.4 yrs), who performed 5 trials of a representative task at four different start distances (1, 1.5, 2 and 2.5 meters) between the defender and the ball (5 repetitions x 6 players x 4 distances = 120 1v1 trials). Players' motion was captured by digital video camera. For image treatment and to extract data on player movement coordinates, we used the TACTO 8.0 software at 25 Hz. Following, we constructed plots with the time-series of these two control parameters candidates associated with the time-series of players' distance to the end line. Graphical inspection showed in all trials a clear tendency for greater relative velocity and lower interpersonal distance values during phase transitions between coordinative states. To confirm this interpretation, we computed a time-series analysis of Z-scores of relative velocity and interpersonal distance data, and a time-series analysis of Z-score differences between these variables. Mean data showed that maximum peaks in Z-score differences were related to all phase transitions.