The current study investigated the relationship between isokinetic knee strength, jump performance, agility, linear and repeated sprinting capacity and Yo-Yo IR1 test performance and the fatigue indices of some of these variables in semi-professional soccer players. Twenty semi-professional soccer players participated in this study, performing 6 tests: bilateral concentric isokinetic strength tests of the knee extensors and flexors (60◦.s-1 and 300◦.s-1), jump tests (countermovement, squat and repeated jumping), linear sprints (10 and 30 m), agility (Illinois test), Bangsbo repeated sprints (7 x 34.2 m), and Yo-Yo IR1 tests. While no isokinetic variables were significantly correlated with field test results, some jump test results correlated with AgiWB, 10- and 30-m sprint times, RSTMEAN and FIRS. Furthermore, the knee isokinetic strength (60◦.s-1 and 300◦.s-1) indices and jump capacities demonstrated moderate to strong relationships with each other. In addition, AgiWB correlated with the 10-m sprint times and RSTMEAN, 30-m linear sprint times correlated with 10-m sprint times and AgiWB, and FIRS and RSTMEAN correlated with the Yo-Yo IR1 test results. The results suggest that power output during CMJ and RJ tests and not isokinetic knee strength are informative in determining field conditioning parameters for semi-professional soccer players.