Monitoring neuromuscular status during high training loads is critical for optimising performance in elite sports. We tested whether the same-day decrements in countermovement jump (CMJ) metrics are associated with slower 10-m sprint performance among professional and elite youth ice hockey players during off-season training. Twenty male ice hockey players (age 18.23±2.46 years) completed 115 testing sessions during the off-season. In each session, CMJ testing on the VALD ForceDecks was conducted before sprinting, followed by six 10-m sprints measured with Microgate photocell gates. The two best attempts were retained. Within-session reliability was assessed from single and average measures, whereas mixed-effects models used the mean of the two best attempts. Linear mixed-effects models quantified within-player associations, with logtransformed sprint time as the dependent variable and player-mean centred CMJ metrics as predictors. Withinplayer decreases in concentric impulse, jump height, RSImod, and concentric peak force were associated with slower 10-m sprint times. Concentric impulse showed the greatest sensitivity: a 10 N·s decrease corresponded to ≈1.4% longer time (≈ +25 ms at 1.77 s). Similar effects were observed for jump height (−2 cm: ≈ +0.9%, ≈ +15 ms), RSImodFT (−0.05 m·s −1: ≈ +0.8%, ≈ +14 ms), and concentric peak force (−100 N: ≈ +0.8%, ≈ +14 ms). Reliability was excellent for 10-m sprint time and primary CMJ performance metrics (ICC(2,2) ≥ 0.93). In applied off-season settings, same-day declines in CMJ, especially concentric impulse, jump height, and RSImod, were associated with slower 10-m acceleration. Therefore, brief CMJ screening may inform session-level speedtraining decisions.