North Melbourne coach Brad Scott has defended the club's decision to play Drew Petrie after the big forward hobbled around in a limp display, prompting questions over why the vice-captain was rushed back into action.

Petrie was held to seven possessions in North's 30-point loss to Sydney at the SCG on Sunday and even Swans coach Paul Roos was surprised to see Petrie take the field in the second half.

"I didn't think he was going to come back on after half-time to be honest because of his (foot) injuries going into the game," Roos said on Sunday.

"And I saw him come off when I was sitting on the bench and he looked pretty dejected and I thought he'd re-done his foot but obviously I'm not privy to what happened to him.

"So I was a bit surprised that he came back on."

Petrie was out for the first nine rounds with a broken foot, then broke a bone in his other foot when he returned against Fremantle in round 10, returning again on Sunday.

"He got medical clearance from the surgeon to play, we had training sessions with him when he looked really good, really strong, but clearly he wasn't right today," Scott said.

"We obviously wouldn't risk him if it was going to do any damage in the second half but the medical guys were pretty confident that he could go out and play at full forward.

"When it became evident to me just from looking at him, and probably to everyone at the ground, that he just wasn't right, we had to take him off.

"We'll assess him and see how he is but I've got no word at this stage until he gets a scan just what's wrong, whether it's a new injury or whether it's an aggravation of the old one."

Ninth-placed North face Richmond at the MCG on Sunday and Scott says his side can't be counted out of finals calculations yet.

"The Sydney Swans ran really hard today, they ran a lot harder than us, and taught us a lesson," Scott said.

"They're mentally injured today. They're really disappointed, and so they should be because we knew what an important game this was and we didn't come out and compete at the level we hoped.

"We had 15 players with 12 possessions or less so against a quality, unified outfit like the Swans it's going to be really difficult to compete against them when you get that sort of output.

"Our forward structure wasn't very effective but our midfield didn't run hard enough either."

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