The Magpies were outrun and outgunned by the impressive Swans, despite setting themselves to back up strongly from last week's excellent win over Geelong.
Buckley's men have not put together successive wins since rounds one and two and, at 5-4, could be out of the top eight at the end of this weekend.
"There's no doubt that we looked like we lacked some pep tonight," Buckley said post-match.
"We were half a step off where we needed to be. Part of that is psychological.
"We didn't rest on our laurels. We set ourselves to come out and reinforce the performance of last week, because we've been up and down.
"We need to be better than that."
Buckley said the Magpies' ladder position was reflective of their performance so far this season.
"I think we've found a level at the moment for what we're putting forward," he said.
"We've played six of the top eight sides, and we've lost four games.
"We need to improve our level in the next four or five weeks to be able to contend and win games against the best opposition."
The second-year coach lamented his team's poor ball use, although accepted that it was in part due to the opposition's outstanding pressure.
He said the Swans had run harder in both directions, meaning they were able to nullify Collingwood's forward line and clear the ball easily from defence, and then hurt the Magpies on the counter-attack.
He pointed to the possession differential inside Collingwood's forward 50, which he said was plus-21 in favour of the Swans.
"That's a huge number," Buckley said.
"Minus-five is a huge number, so minus-21 really tells you how dominant they were when the ball went into our forward 50.
"They ran harder back to protect their defence, and they ran harder forward.
"We just didn't work hard enough; we were caught in the middle."
The Magpies will have a chance to gather some momentum against lower-ranked opposition ahead of their round 13 bye. They meet the Brisbane Lions at the Gabba next Friday night, followed by winnable games against Melbourne and the Western Bulldogs.
