We examined changes in the haematological, metabolic, immunological, hormonal, and psychological fields using selected variables in 20 professional soccer players. over the course of a competitive season. The team performance was assessed by computing the winning percentage. A symptom checklist was used to assess the severity of upper respiratory tract infections. A high-intensity training programme induced a significant increase in cortisol and uric acid concentrations. Despite lower glutamine concentrations than the normal range throughout the study, infection occurred only in two of the soccer players. Moreover, the levels of immunological factors IgA, IgG, and IgM, and the haematological parameters were unaltered. Subsequent decreased performance coincided with changes in specific mood states of the team. Our results show some alterations on the metabolic, hormonal, and psychological variables over the five fields studied, suggesting that combined psychological and physiological changes during training are of primary interest to monitor the training stress in relation to performance in team sport.