If players are going through practices and not screwing up in multiple areas then it probably means they are not practicing correctly. Typically the player not making any mistakes in practice is simply using practice as a way to maintain himself at his current ability level. This is a dangerous approach because, as I said in a previous post, winners are always chasing something. A player who maintains is a player standing still and therefore easily chased down.
Want to get better? Start making more mistakes!