Collingwood coach Mick Malthouse has blamed a huge number of forced team changes for the Magpies' flat performance against Brisbane on Saturday night.

But the experienced Magpies mentor says the reigning AFL premiers need to snap back into form fast, warning his team they can not expect to automatically find top gear in the finals.

While Collingwood won 14.18 (102) to 13.6 (84) against the Lions at the MCG, poor first and last quarters were a concern.

The Lions led by seven points at the first change and while the Magpies dominated the middle stages to lead by as much as 48 points early in the last term, they then eased the pressure, allowing Brisbane seven last-quarter goals.

"It was played spasmodically really," Malthouse said.

"We were good and we were poor, we were quite effective and we were very ineffective, we were quick and we were slow, we were clean and we were fumbling, we were good defensively and we were quite poor defensively.

"It was a game of contrasts for us."

Midfielders Dane Swan, Scott Pendlebury, Luke Ball and Dayne Beams were all solid performers, with Swan in particular in outstanding touch, while key forward Travis Cloke impressed with five goals.

But, after making six team changes, five of those due to injury, Malthouse felt Collingwood's defensive intensity suffered.

"The side changed quite significantly because of numbers and I half suspect that the pressure mounted on too few," he said.

"As a consequence, when you control the ball it's not too bad, when you don't control the ball you need to split that, share that (responsibility), and I don't think we did really."

He said the fact that Collingwood laid just 46 tackles for the night, well below their previous season low of 55, showed how much their defensive pressure slipped.

Six members of Collingwood's best side missed the game through injury, including late withdrawal Andrew Krakouer (quad), along with the suspended Heath Shaw.

Key defender Ben Reid was subbed off at three-quarter time, after copping a heavy knock to the back in a marking contest, although the Magpies were confident he had not suffered structural damage.

But Malthouse said the rash of injuries was a worry.

"Any injury's a concern and when you get multiples, of course they are."

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