Abstract
This study examines the influence of game speed and the tactical efficiency of offensive actions on the performance of junior football players aged 12–13 years under small-sided game conditions. The research included 24 official matches played by an elite team (ET): 12 during the first half of the competitive season, representing the initial assessment, and 12 during the second half, representing the final assessment. Between the two evaluation stages, a specific training programme was implemented to develop execution speed, optimise offensive transitions and improve ball possession, passing accuracy, and finishing ability. Performance was assessed using the Game Speed Index (GSI%) and the Tactical Efficiency Index (TEI%), calculated through video analysis. The GSI increased from 57.06% to 77.28%, while the TEI rose from 51.11% to 75.86%. These findings indicate a direct relationship between an increased game tempo, improved tactical efficiency and the effectiveness of finishing actions.