Yeh, but to argue with myself, while I can understand Cooper not trusting Drouin 5v5, there was no logical reason not to have him on the first power play. Koekkoek is a riddle, somehow Cooper trusts him in the ECF when everything is on the line and then the next year he trusts him less than Nesterov? Riddle me that. Then at the end of the year a rookie Dman ends up on the top pair. I'm not being uncritical, I'm just saying, whatever the biases is, it is not just against youth. There are too many instances that disprove that.
Context matters though. Nesterov was brought in for a very specific reason at the time: Improve our offense. He has the ability to carry the puck up ice and create scoring chances. Also, showcasing him for trade-bait. Dotchin was brought in as a bandaid but had instant chemistry with Hedman, isn't terrible defensively and neither offensively and will play the body without hesitation which helped our rather soft lineup. So he immediately stuck.
Koekkoek seemed overwhelmed at times and had trouble with physical opponents. They decided he'd benefit more from playing in the AHL in a top-4 role than playing passenger on the 3rd pairing 2/5 games a week in the NHL.
As TampaJay pointed out Cooper is pretty consistent when it comes to rookie forwards. If they are solid or at least not a liablity defensively they'll get a fair chance and more than one. See Johnson, Palat, Kucherov, Point, Namestnikov, Gourde etc. The opposite can be said for the likes of Drouin, Panik or Connolly who regularly let the foot off the gas the moment we lost the puck.
When it comes to vet players though Cooper's decision making is questionable at best, see Killorn, Filppula, Morrow, Garrison, ...