It's an widely acepted sequence in the learning process. Also part of this is that you can only ever really learn by failing. The failing is what provides the stimulus to correct and refine. So it's not optional and you can't go from being rubbish at something to being great. Learning anything is just a system of repeated failiures which become less and less over time. This is all under the caveat of having foccused/structed learning that identifies the mistakes.
The key is to have the goals attainable but just slightly beyond your skillset. In this instance I guess we'll get rid of player who's skillset is too far the level we need, and who's approach to learning isn't in sync with development. Those who remain will continue to practice, learn and ultimate fail less until those 10-15 minute periods are 30 min periods and full games.
Then we'll see what is what.
The best recent example really is Arsenal from Arteta's arrival. Shipped players out, new ones in. Went from crap to less crap to good. What is also interesting is that he himself has undertook this process and is a lot more flexible now, making comprimises to win games. Whether Ange will is going to be interesting.