Read.
If you want one player to play 48 mins and set him in all slots on that position and dont have more then 9 players (two for each other positions) you will get 48 minutes in 99 out of 100 games.
The thing is that in case you wnat him to play (for example) PG as starter, SG as backup and PG as reserve, there is a chance that he will not get (I believe) that 48 minutes, and I believe that he should have also on that case.