There are 3 games a week. Make sure you play your trainee at 48 minutes (list him at all 3 spots in the rotation)at PG during the cup game. When you're out of the Cup, make sure you schedule a scrimmage every week and play him at 48 minutes against that team.
And actually, if you're doing single position training, I would suggest getting 1-2 more solid guard trainees and also play them at PG. Then play the PG you like as the starting SG. This will maximize your training routines.
Read the manual to learn about game shape too. You shouldn't be playing this starting PG as the starter 3 times a week or he's simply going to get progressively worse as the season wears on due to overuse. You only want to play him a total of 48-75 minutes a week.