This study investigated how varying task constraints - pitch size and the presence of a goal - affect psychophysiological intensity, technical execution, and tactical decision-making in small-sided games (SSGs). The study also examined correlations between intensities and technical and tactical performance. Thirty-six regional-level male youth soccer players (aged 16.5 ± 0.5 years) participated in a four-week intervention using a non-controlled, repeated-measures design within a single cohort. Players completed 3v3 SSGs under six conditions combining three pitch sizes (75, 100, and 125 m² per player) and two task goals (ball possession vs. small goals). Each session included standardized warm-ups and three 4-minute bouts per condition. Psychophysiological responses were measured via Rating of Perceived Exertion (RPE) and heart rate monitoring (HRmean, % time in Zone 5). Technical actions (passes, receptions, dribbles, shots) and tactical decision-making (Passing Decision-Making index) were assessed through video-based analysis. Significant interactions (p < 0.001) between field size and scoring method were found for HR measures and passing. Ball possession games showed higher HRmean and HR Zone 5 across all field sizes compared to small-goal games (p < 0.001). However, even in small-goal games, HRmean and HR Zone 5 significantly increased with larger field sizes (p < 0.001). Small-goal games resulted in more successful dribbles (p < 0.001), with fewer successful passes on the smallest field. A moderate negative correlation was observed between HRmean and successful shots (r = -0.346, p = 0.039), and between time in HR Zone 5 and the passing decision-making index (r = -0.363, p = 0.029). The study suggests that both field size and scoring method significantly influence players’ physiological responses, technical performance, and decision-making. Ball possession games and larger fields increase physical intensity and passing success, while smaller fields and small-goal games promote dribbling. However, higher physiological strain appears to negatively impact shooting effectiveness and decision-making quality, although these correlations are moderate and no definitive conclusions can be drawn or generalized.

• Higher heart rate intensity - especially in larger fields and ball possession formats - correlates with reduced technical accuracy and tactical decision - making quality in small - sided games.

• Small - goal games promote successful dribbling and lower physiological load, while ball possession games increase heart rate and passing frequency but may impair execution and decisions under fatigue.

• Manipulating field size and scoring method can balance physical demands with technical and cognitive performance in youth soccer training.