What I keep going back to is "fit". For example, most of us seem to now be of an opinion that Granger's presence greatly enhances the performance of our starting unit. Although, I will give George and Vogel major credit in that they have made major advances over the last 5-6 games in adjusting george's role to help the performance of the starting unit.
And the same is true for the bench. The only difference is that the player's aren't nearly as skilled, therefore the learning curve will probably be longer. The things I feel confident in concluding are:
DJ just doesn't fit into the second unit. His performance in a half-court game has been abysmal. And, especially after attempting to improve the defense of the second unit, it would make sense that we want a backup PG whose strength is half-court play in order to help slow the game down while still being able to initiate plays and directing the offense towards good, patient shots. And thus far, those strengths don't appear to play into DJ's bag of tricks. Ben, OTOH, although drawing a conclusion after only one game, appears to have that strength while also being a much, much better defender than DJ.
I'm not blaming DJ because based on his prior season, it seemed that we were getting a great player for the second unit whose glaring weakness (defense) was going to be well-compensated by other players acquired for the second unit. Unfortunately, those in his camp were wrong because DJ has played enough games to show that he just isn't going to fit.
As for Young and Mahinmi, they have greatly bolstered the defense of the second unit and have enough offensive skills to warrant saying that they will eventually prove to be good fits. I would go as far to say that Ian could step in as a part-time starter if Roy had to sit a handful of games.
Green is the puzzle for me. His ball IQ is horrendous; he's probably more "deer in the headlights" than Bender ever was. I guess I'll just say that Greens usefulness is totally dependent on the PG that is on the court with him. If we have a PG with decent half-court vision that can penetrate the lane, then opportunities for Green could be created to accompany the few opportunities that can be provided for him on fast breaks. If not, then we need to find a cave for Green on another team where he can hibernate.
At any rate, I think that the ability for a player's skills to blend with those of his teammates is even more important than the statistics he presents while playing for other teams. Using that criteria, we may have gotten a couple of keepers. But then again, we have also probably picked up a couple of duds, too. It might very well come down to how well we can settle the PG position in the second unit.