An observation I've seen is that athletes that are a little sore in the legs (quads, glutes, hamstrings) sometimes perform better in a vertical jump test. I've been testing vertical jump at different times throughout the practice and training week of teams, and have notice some improvements in vertical jumps the day after a relatively intense in-season lifting session. There hasn't been massive increases of inches, but some athletes have jumped 1-2.5 inches better, and teams have improved as much as an average of around .25-.4 inches. Obviously this means some athletes had slight decreases, but I can confirm it's very rare.
Not sure for the specific mechanisms as to why this occurs; I could conjecture that the soreness creates stiffness in the muscle and 'tugs' on the tendons a bit more, tightening the "springs"??? Musculotendon stiffness leading to increased elasticity? The CNS still running 'hot' from the previous day? Maybe the previous testing time was a poor performance?
What this all means, I am not quite sure, but the athletes and teams continue to performing well; and most importantly we are not injured, beyond small things that don't limit playing or practice time. The correlation I do see with this is that, the good teams and coaches continue to attempt to develop their team throughout the in-season with intense practice and progressive in-season strength and conditioning. There is the necessity to control volume, but intensity must stay if not push higher. The reason this can work is tracking the general volume and most importantly practicing the lost art of common sense. Verbal, face-to-face communication amongst coaches and athletes really does go a long way.
With the "survival teams" (teams struggling), there is the mentality of so-called 'peaking' for every game and unfortunately at times for every practice. I have noticed an increase phobia of soreness in-season, and the problem with avoiding soreness is we always stay behind the soreness "wave" and never catch the surf to be ahead of muscular discomfort from being more adapted.
There are few times in a season that team sports really need to taper and peak, and these dates need to be highlighted; the quest should be for constant development in-season and out of season. Dynasty's are never built tapering for everything, when there is nothing to ever taper from; there is only a few play-off games each season, and only one Super Bowl or championship... and if it takes treating every game and practice as such, then you probably aren't good enough anyway and should get back to work on the basics of technical, tactical, and physical development.
Record keeping and common sense.