The Bombers trailed last year's premiers for most of the day before grabbing a lead they would never relinquish at the eight-minute mark in the last term.
Adelaide now looms as Essendon's elimination final opponent.
Knights, who looked exhausted after the match, said the journey had been a long one, especially after the side lost its primary ruckman to a season-ending knee injury in round one.
"It's been a pretty big run in to this scenario, for about six weeks now," he said after the match.
"To come down to the last round of the year, against the reigning premiers, I said to the boys during the week it was pretty exciting to be involved in a game like this.
"For our young players to play in front of a huge crowd today and come through and get the result was good for our development".
But the coach does not believe just making up the numbers in the finals is enough for his club.
"I said to the players I felt they'd really earned their finals spot, particularly post the West Coast and Richmond games.
"We played Brisbane, who are a top five or six side, and we've played St Kilda, and we played the reigning premier in the last round [and won them all].
"I've felt over the last month we've grabbed hold of that eighth spot now and we deserve to be there.
"It's great for the players to reward themselves with a final in this season, but we've got to now make sure we have a solid impact in the finals.
"It's not a satisfaction that we've made it now, we've got to try and make a bit of a splash and really go after trying to get a win next week."
Michael Hurley, who was the youngest Bomber on the ground at 19 years and two months was another cause for excitement for the coach.
"I've got to hold it together a bit when I talk about Michael Hurley - I get a bit of grief already about talking pretty positively about it," Knights said with a smile.
"We wrestle at match committee about whether he's going to be a centre-half back or a centre-half forward – mind you, it's a good discussion to have because someone of that quality can play at both ends.
"But I guess when you see a young man take a contested mark and turn on his left foot from 50m out ... you've got to really appreciate that.
"That's just a fine bit of football."
