Study aim: To assess changes in physical fitness of amateur soccer players after a pre-season training period and baseline fitness dependencies.

Material and methods: Twenty-one amateur soccer players were assessed during the pre-season. The following physical variables were assessed before and after a two-month pre-season training period:(i) cardiorespiratory fitness,(ii) strength and power, and (iii) change of direction (COD).

Results: Significant decreases were found for countermovement jump (CMJ)(p< 0.001; d= 1.161), drop jump (DJ)(p= 0.014; d= 0.958), and horizontal jump (HJ)(p= 0.042; d= 0.640), while no significant changes were found for the overall variables from the beginning to the end of pre-season. Fit players revealed significant decreases for CMJ (p= 0.002; d=–2.495), DJ (p= 0.004; d=–1.760), HJ (p= 0.028; d=–1.005), COD deficit (p= 0.034; d= 1.013), and maximal aerobic speed (MAS)(p= 0.026; d=–4.053). No significant changes were found for unfit players. Conclusions: Amateur soccer coaches should consider assessing physical qualities at the beginning of pre-season and use the free-of-charge monitoring tools such as session-rate of perceived exertion (s-RPE) during the training process.