Monitoring athlete readiness in youth rugby players is important for understanding short-term responses to match demands and supporting recovery management. Here, we aimed to investigate short-term readiness by integrating subjective measures, clinically relevant tests, and match load data. This single-team study considered 28 male rugby players (17.8 ± 0.2 years), monitored every four consecutive days (match day [MD], MD+1, MD+2, MD+3). Readiness was assessed using four subjective dimensions (fatigue upon waking, mood, sleep quality, and muscle soreness), which were normalized to individual best values and combined into a composite readiness index (4-dRI; 0–1). The Adductor Squeeze Test (AST), Sit-and-Reach Test (SRT), and Global Positioning System-derived metrics (MD only) were also assessed. The 4-dRI decreased by approximately 30% at 24 h post-match (p < 0.001), indicating a substantial reduction in perceived readiness. Athletes exposed to higher GPS-derived match loads reported lower readiness on MD+1. AST showed moderate associations with the 4-dRI (ρ = 0.40, p < 0.05), whereas SRT appeared less responsive to short-term changes in readiness. These findings indicate that both the 4-dRI and AST were responsive to short-term changes in readiness across the competition period. Overall, these integrated data may contribute to athlete-monitoring strategies in team sport settings.