Collingwood forward Alan Didak has been ruled out of his side's crucial AFL clash with North Melbourne on Friday night because of injury.

Didak did not train with his teammates on Thursday - coach Mick Malthouse later confirming it was because of a lingering hamstring problem.

Didak aggravated the injury at training earlier this week.

"It's definitely a hamstring. He might miss a couple of weeks," Malthouse said.

But defender Heath Shaw looks almost certain to return after training fully to dispel doubts about his suspect hamstring.

Captain Nick Maxwell will also return from suspension for the Magpies.

Both sides have 2-3 win-loss records going into the match at Etihad Stadium.

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