This project investigated effects of 8 weeks of biweekly loaded combined plyometric and short sprint with change-of-direction training an in-season regimen of young soccer players. An experimental (n = 17, age: 16.5 ± 0.5 years, body mass: 64.5 ± 5.2 kg, height: 1.73 ± 0.07 m,) and control group (n = 17, age: 16.7 ± 0.5 years, body mass: 65.6 ± 4.8 kg, height: 1.74 ± 0.07 m) were tested pre- and post-intervention for squat-jump (SJ), countermovement-jump (CMJ), and five-jump test (5JT), 10 m and 30 m sprint performance, change-of-direction ability, and dynamic balance performance. The experimental group (EG) outperformed the control group (CG) over 8 weeks in jumping (p < 0.001; d = 0.98–1.17), 10 m sprinting (p < 0.001; d = 0.94), change-of-direction ability (p < 0.001; d = 1.24), and dynamic balance performance (p < 0.001; d = 0.53–0.74). We conclude that adding biweekly loaded plyometric with short sprints and change-of-direction training to habitual training improves athleticism of young soccer players. Therefore, loaded plyometric with short sprints and change-of-direction training should be implemented as a part of research-informed soccer training.