"Niko can do better," Adams told The News.
"He knocked in a few goals last season, but he hasn't scored since he was a super sub a couple of months ago, though.
"I expect more from my great players, because they are great players and Niko is a great player.
"I want to stretch my players, always push them and I think he is someone who needs that.
"He is a great footballer and needs to keep delivering."