
I think the three-headed GM's guiding principle was to keep veterans
in favor of youngsters only if they offered a "significant" advantage.
At the end of last season, the contracts of several veterans with somewhat
maginal contributions (Fenton, Bozek, Anderson, and a couple others I
can't remember) were bought out. The idea was that youngsters could
play almost as well, and had the potential to improve where these
older guys did not. 
And they traded Mullen, because he wanted to go, not because he
wasn't good enough, but I think they were a bit too optimistic
in thinking they could make up for his contributions.
An example from this season, Skriko was brought in on a trial basis
but not kept, because of his age. I thought he was a decent
contributor worth keeping around.

The youth movement has its advantages; look at Gaudreau who
might still be in KC if more veterans had been kept around. But
you have to find the right balance.