I ran "Strictly Follow Depth Chart" And I had my PG and Backup PG the same guy, it subbed someone in for him in the 4th Q in a blowout game... Earlier this season this happened. Why?
If you're referring to your last league game, it was because you had someone on the bench that was not assigned as a starter or backup for another position. If you want one guy to get 48 minutes, you can field a maximum of 9 players, with the following type of setup:
PG: 1-1-1
SG: 2-6-6
SF: 3-7-7
PF: 4-8-8
C : 5-9-9
In garbage time, the coach looks to take starters out whenever possible. While it's impossible to completely prevent this while fielding any substitutes at all, if you follow the above then you have the best chance of getting 48 minutes for your PG. It's still not foolproof - sometimes he'll be subbed out very late, especially if he's got stamina issues, and if you get the "It looks like we are now in garbage time" notification while one of your other starters is going to the FT line, that starter's backup will replace your PG.