A seamless transition into senior football has underlined the 19-year-old winger's undoubted talent and McKenna believes City are witnessing the first steps of a special career.
"Robbie has been a great signing, he's a great asset," McKenna told the Hull Daily Mail.
"For it to be his first season in senior football he's done unbelievably well.
"He's going to have games where sometimes it doesn't go for him because he's that creative but he's been outstanding for us.
"He can probably try too hard sometimes but that's the attitude that will take him to the top.
"I can only see him being a top, top player because he's got huge ability and his work-rate is phenomenal as well."