I don't think Danny or Doc are expecting Darko to transform into anything all that much different than what he has been. One thing that I believe you can expect from Darko based on his track record is durability (same for Collins).
If you consider what issues the Celtics have had with durability of centers (Perk, Shaq, Jerm,...) then you can see why durability is very attractive to them. Over the last say 4-5 years we have done really well whenever we had even a decent center that was healthy and on the court (allowing KG to play PF).
Did you say 'durability'? Darko's track record in durability the last 5 years:
2011 29 games played
2010 69 games played
2009 24 games played
2008 61 games played
2007 70 games played
Darko has NEVER played a full NBA season in his career, his season high being 80 games. If we calculate his average over the last 5 years that would be: 50.6 games per season or 61.7% of possible games played. Or another way to look at it 38.3% games missed per season.
The only good news is that Darko is still relatively young at 27. But the guy has been known to miss games, particularly over the last 3 years. When healthy though, Darko provides intimidation in the paint. He's a tough 7 footer who likes to bang and won't back down against anyone, just watch the youtube video where he knocks down Perk. And that is a BIG man he knocked down.