Purpose: To investigate the effects of a match-congested period on straight and curve sprint performance, change of direction (COD) speed and deficit, vertical jumping ability, and half-squat (HS) mean propulsive power (MPP) output in young soccer players. Methods: Fifteen under-20 elite male soccer players participated in 14 matches over 8 weeks. The following assessments were performed before and after the congested fixture period: squat and countermovement jumps; 17-m linear sprint; curve sprint (CS) test for the “good” (CSGS) and “weak” (CSWS) sides; modified 17-m Zigzag test; and HS MPP. Magnitude-based inferences and a paired t-test were used to analyze pre-post changes in the assessed variables. Results: Very likely (P < 0.05) decreases were noticed in 17-m sprint velocity (ES [90%CL]: -0.56 [-0.32; -0.81]) and CSGS (ES [90%CL]: -0.72 [-0.40; -1.03]) after the 8-week period. A possible but non-significant impairment was revealed in CSWS (ES [90%CL]: -0.18 [0.03; -0.39]) and CMJ (ES [90%CL]: -0.21 [-0.54; 0.12]). Zigzag velocity (ES [90%CL]: -2.90 [-2.45; -3.36]) and COD deficit (ES [90%CL]: 0.86 [0.52; 1.20]) were almost certainly and significantly (P < 0.05) reduced and increased, respectively, after the match-congested period. An almost certain and significant (P < 0.05) reduction was found in HS MPP (ES [90%CL]: -1.18 [-0.76; -1.61]). Conclusions: Straight and CS velocity, COD speed and deficit, and HS MPP were impaired after the match-congested period. Vertical jump height was possibly decreased. Seasonal phases comprising high volumes of soccer-specific training and competition seem to be detrimental to speed-power qualities in under-20 elite soccer players.