If Kemba went down the 2011 team was screwed. If Baz went down the 2014 team was screwed. Any team that loses its three best players is screwed.
Totally agree on size and physicality. Incoming guys are an upgrade in height at least. Expecting some more muscle on Josh and Tyler. Both got stronger between freshman and sophomore seasons. Sid needs to get stronger and work on his shot. But at least we won't try to make him play as a 4 anymore. Polley needs to do what you said, but those deficiencies are very different in a 12-15 minutes a game guy vs 27 mpg. Vital has major deficiencies too, and the fact that he played 30 minutes a game exacerbates them. He won't be getting 30 minutes next year.
If you can't expect your staff to get incremental year to year improvements from players then fire them. You cannot win in college basketball without that, unless you bring in a class like Duke had last year. Most good high major teams are relying on freshmen to contribute along with 3* guys that developed. I think the three freshmen we have so far will all play a lot, and they will have some early bumps, and be solid by the end of the year.
Last year's Tennessee team starting 5 was all seniors and juniors who were 3* recruits. They were guys a lot like Vital, Carlton and Polley who played a lot early and kept getting better.
Tennessee 2016 Basketball Commits Look at Houston. Rob Gray 3*. Armoni Brooks 3*. Corey Davis - 2* or unranked.
All that being said, if Diarra really can't play we need to free up that roster spot. If he can play, fine. He's got talent and some of the physicality we need.