Rookies that come into their first year of professional sports often have a lot thrown at them but through good coaching, along with a reduced playbook, and having realistic expectations put in place . This combination often allows a first year player to have some success but can compromise the efficiency a coaching staff may be looking for.
It is easy to understand how this process would need to work. Just watching high school vs college basketball vs the NBA you can see the game speed picking up as the level of competition improves. Second year players like Nikola Jokic and Emmanuel Mudiay would have been just juniors in college 20 years ago.