Yeah, it doesn't matter if you're fit enough to run an ultramarathon, if you can't make quick turns and rapidly change direction. Blaszczykowski is one recent example. Monster of a player in that peak season when BVB made CL final. Relentless when defending, wicked shot with each foot, **** of a dribbler. Then he ****** his knee, out for 9 months, eventually recovered and kept playing for 6 more years but he was never the same. And by all accounts he's a consummate professionals who is always in top shape, but sometimes your body just can't do what you want it to do.