The game was effectively over at the first break when the Pies lead by 44 points, and although the Bombers almost matched them in the second term, the Pies kicked seven goals to four in the second half to consolidate the percentage boost.
But despite the Magpies kicking 18 goals, Knights said the problem wasn't with his defensive group.
"I think the least of our worries, or my worries, are our back six or seven," he said after the game.
"It's the midfields and forwards - when you've got the opportunity when you're going through the corridor and you've got the last kick inside 50, and you've got time and space, you've got to make that kick in this game.
"At the worst you halve it when it goes in there, but at the moment, from 70 metres and in, we're not hurting the opposition with that last kick or last disposal.
"When we're going inside it's coming out too quickly, and it's putting Cale (Hooker) and Tayte (Pears) and Dustin (Fletcher - Essendon's tall defenders) under all sorts of pressure.
"That's what I was alluding to - it's not my back seven, they're not my issue.
"It's our disposal inside forward 50 - it's not productive enough, and when it goes in there it's coming out too quick."
The Bombers have slumped to 13th on the ladder on the back of a 1-4 start, with the one win coming over an unconvincing Carlton - a side Essendon seems to have the wood on - in round three.
Knights said a variety of issues cost his side the game.
"It's a really broad one - it's not one thing," he said.
"There wasn't one quality that stood out that definitely decided today's game, it was a number of thing, whether it be the stoppages, we didn't take the ball cleanly, we didn't kick the ball well, our handballs were to players who were flat-footed."
