"Eden has made outstanding progress this season," Holland said.
"There are only three things a player can do when you get down to the nitty-gritty - make goals, stop goals, score goals. There's nothing else - it's one of those three.
"I think this year he's improved at stopping goals and he's improved at making and scoring goals. So the three productive elements to his performances, there's been a significant improvement in each area.
"Of course he's only a young man. Our expectations are high. It was his first year in the Premier League last year.
"You would hope there would be an improvement this year, and then an improvement again next year.
"He's had a major impact on our season to date."
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