The purpose of the present study was to investigate adaptations of precompetitive training program period on several performance-related aerobic and anaerobic indices in professional soccer players. Fifteen professional soccer players (age 22.2+/-3.27 years, height 180.53+/-5.50cm, weight 78.08+/-5.57kg; training experience 13.60+/-2.44 years; mean+/-SD), participated in the study. Subjects performed countermovement and vertical jump tests (CMJ and VJ) and incremental pseudo-ramp test protocol with measured maximal oxygen consumption (VO2max) and anaerobic threshold (ANT). Modest but significant improvement (p<0.05) of aerobic performance was observed after a 9-week precompetitive training period, with the 6,67% and 7.28% degree of change for maximal oxygen consumption and anaerobic threshold, respectively. Anaerobic power remained unchanged. These results suggest that preseason training can affect aerobic energy system. However, implementation of additional high intensity intervals as well as greater volume of explosive training exercises may be required.