"On the back of our skipper (Ablett) being off …. and no rotations late, I don't think it was our best win as far as the way we played, but our most courageous, clearly," McKenna said.
He said his young team had learned to persevere under duress.
"As long as you're solid in the contest and you can halve those contests like we did for most of the night, you might be able to pinch a win," McKenna said.
"The perseverance and the courage to keep running until the final siren blew was certainly a sign of growing up tonight."
He paid credit to tall forwards Sam Day (four goals) and Tom Lynch (21 disposals and two goals) for continuing to create contests and give his team a chance.
David Swallow (31 disposals) was brilliant all night, while Harley Bennell (26) and Jaeger O'Meara (25) lifted dramatically after slow first quarters to lead an increasingly dominant midfield.
McKenna described it as a "coming of age" and sign of growing leadership beneath Ablett.
"There's a void there because Gary's very good at that," he said.
"He's coached from day one and he continues to coach the boys on field, but those boys were able to step into the breach and carry that through by actions rather than verbally.
"You take confidence in the group that these boys have grown up."