In the future, I predict the top teams who don't want to add to their expenses by increasing skill on their players will value experience more and play older players who train only very slowly (if at all) alongside trainable players to make sure only the players they want trained are trained, while protecting the quality of their roster.
In fact, it is really this season where we may start to see that happen.
For the first time, there may now be enough good players aged 27-30 who are no longer good for training but have average+ experience and do better on court than younger players with similar skill levels.
Further, i the transfer market stabilises, these top 27 year old players will start to become available in the 2mil-4mil range, or about half their worth if they had the same skill and they were 22-24.
And so on, scaling down in skill and cost through the divisions until you get to the level where teams are still kenn to add as much skill as possible through training (that they can afford).
Thus, the game doesn't need a "no training" option - there is already a mechanism in place (albeit requiring a trade off). This game is full of such trade offs, that is why it is good :-D