THE MAGPIES' positive mindset took a tumble during Sunday's 33-point loss to the Western Bulldogs at Telstra Dome, midfielder Ben Johnson says.

Johnson said the players were upbeat and looking for their fourth consecutive win before the match began, but soon became "flat" after the Bulldogs began to nudge their first-half lead in the third quarter.

"The mood was pretty good before the game, and we were pretty confident," Johnson told collingwoodfc.com.au after the match.

"The first quarter was even and then we got up a bit in the second, but I just think the boys were a little bit flat and they ran over us in the second half.

"I'm not sure why we were flat, but I think the main problem was we just let them run. When they do that, they're the best at the running game, so we just had to close them up a little bit more and play more our style, but we didn't do that."

The Pies took a 17-point lead into the second half, and Johnson said the discussions that took place once the side retired to the rooms for the long break were simply about maintaining that sort of difference.

He was at a loss to explain why such a different side came out afterwards, and said it was particularly disappointing considering the fine form the Pies have shown in their final terms this season.

"Half time was all about game plan stuff, maintaining it, and keeping the pressure on," he said.

"But when we went out, we were a different team after half time.

"It was only 11 points at three-quarter time and you're always in with a shot. They might have been thinking was it slipping away for them.

"You can always come back, especially with the way we've been playing our last quarters recently, but we were flat and it was just one of those games.

"As soon as you let them run, they'll just kill you."

Johnson spent much of the afternoon filling a defensive role opposite Brownlow medallist Jason Akermanis.

The Magpie said he felt he performed "okay" against the triple premiership player, and hopes his 17-possession game is the catalyst he needs to get his season back on track after an indifferent start that was affected by injury.

"I went back and I haven't done that for a couple of years now," he said.

"I did okay. I think he kicked a couple of goals, I know one wasn't on me, but one was over the top when I had to go to the player and they kicked it over the top.

"I haven't had the best season so far, but I'm confident I'll get back up there. I haven't been training all year and this week was the first week I've been able to train because of the ankle.

"That's better now, and I just need a few training sessions. I lost a bit of fitness, but I'll get that back."