McKenna worked with Greenwood within United's academy.
He said: "It's great timing for Mason that he's been able to work under such a great striker in Ole.
"There aren't many better than Ole in the history of the football club for goals in the penalty area, the different type of finishes from inside the penalty area, anticipatory movements in the box.
"Ole was really strong and passionate about that and it's something for Mason to work on."
McKenna added: "As finishers, in terms of left foot and right foot, Ole sees similarities between him and Mason and that probably helped with their bond and his willingness to push Mason and give him the opportunity.
"Likewise, for Mason to know when he's getting advice off the manager, it's from someone who has been there in the penalty box and done it. It's a really beneficial relationship for him.
"Mason's lucky with the manager that he's come under - not just in terms of goalscoring, but how he handles him as a person, as well. He's been fortunate he broke into the first-team under Ole."
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