As others noted, veterans Kelly and Gerald have yet to play.
Further, in reality, once the regular season starts, Brad is not likely to leave the bench hanging out to dry with just the youngest players out there for long stretches like he did in the 4th period of the pre-season. That's just something to do now, for development.
Not only will the starters consume another 10-12 minutes of game time compared to that night, but more than likely they will be staggered to overlap with the bench. I.E., I expect one or two of the starters to stay on the floor for the first few minutes some bench players come in and I expect one or two of the others to come in early before all the bench players have subbed back out.