"People who used to see Ma'a as just a big ball carrier and that's sort of his dimension … it's been good being able to train with him to see his skills, to see his feet and his hands are all still there," Collins told Radio Sport.
"He's been really good. A bit like Sonny to an extent, I guess. Those guys who have been around the tracks but obviously taken very good care of their bodies and just have that professional side where it's a good show for the younger boys.
"It creates competition in midfield and in the backline in general and it's good for everyone."
One of the players Nonu will be trying to keep out of the starting XV is TJ Faiana.
The 23-year-old was one of the standouts in Auckland's successful Mitre 10 Cup campaign, his performances in the blue and white hoops forcing him firmly back into the Super Rugby frame after sporadic appearances over the last two years.
"The competition is good for the team. Having two All Blacks makes me want to go up against the best and that is a good challenge," said Faiane.
"Sonny over the last two years has been awesome for me. Ma'a I've just met and he's been good to me as well. He's super competitive, a ball of energy. Both of them are always willing to help and that's the main thing."
The transition from to a new coach has been surprisingly smooth, said Collins.
"I'd say it probably would've been pretty tough early on for them [Umaga and MacDonald] but full credit to them. Their dynamic is just really good with him and Tom Coventry and Tana are pretty close off the field.
"They've put their individual stuff aside and work together for the team. There's been no disconnect there which is awesome for us."