Saying they lost a lot is an understatement to say the least.
They lost three potential lottery picks. What other team lost that type of firepower? That frontcourt was everything to them. Just ONE of them missing would have changed their season. I'm sorry, but losing all three, plus their normal graduating seniors(Barnett, most notably), that's four starters gone. No way they reloaded to a point where they can be just dropped into the top 5.
Now, can they come together and be a top 5 team? Absolutely. The talent is there to be very, very good. There are a lot of teams like that. I look at Louisville. They loaded up, but nobody is making any assumptions on anything with them.
You just don't lose an NBA roster and pick up where you left off. May is a really, really good coach, but he didn't have to be John Wooden to win with that team last year.