How rusty do you get after missing some time from basketball?
The answer to this question often depends on what sort of base you have. The longer you have played consistently, the less rust you are going to have and the quicker the rust will come off once you get to play again.
In the NBA, we have seen players that seem to bounce back from serious injuries immediately (Chris Paul) and players who may take even years to get back into form (Kevin Garnett.) This rebound has to do somewhat with age, but also with the type of injury {Paul had a tear, usually easier to come back from (though also more serious in that it is can more easily lead to another serious injury) than wear and tear injuries like Garnett's.)
How do you rebound from injuries and time off?