Even if Carr isn't a "true" PG, at this point, he might still be the best PG on the roster.
I'm sure the master plan involved Washington playing the most minutes at PG this year, with Coffey as the back-up plan. Washington's issues, whatever they are, have led to the current situation. As a coach, you hope for the best, but you always have to have a plan in case of the worst.
It just reinforces the feeling that Pitino and his staff really believed Carr would get the waiver and be able to play this year. If they knew going in that Carr would not get the waiver, I suspect they would have done something different.