North Melbourne had just about put a line through Daniel Wells playing any part in the final quarter, before the veteran midfielder bobbed up and played a pivotal role in the Kangaroos' seven-point win over St Kilda.

Wells suffered a "significant cork" in the third term of the game at Etihad Stadium and the club's medical staff was content to put him in cotton wool for the rest of the game.

North coach Brad Scott believed that to be the case too, but was buoyed when Wells put his hand up to return to the fray in Drew Petrie's 300th game.

"[The doctors] weren't keen to put him back on but they did say, 'If push comes to shove and you need him then let us know,'" Scott said after the match.

"Push came to shove and I said, 'Now would be a good time'.

"I had probably moved on – that sounds callous I know. But I'd made the decision that we've got the three on the bench and we'll have to go with them."

Wells laid two important smothers in the final term and won a crucial ball in dispute at half-back as the Saints came charging home.

"'Wellsy' just willed himself to get back on and I spoke to him afterwards and he said he wasn't going to let [the game] slip," Scott said.

"Whatever he had to do he was going to do and I think that again shows what they (the players) think of Drew."

Shaun Higgins also had an injury scare when he hobbled from the field after Saints defender Sean Dempster fell across his right knee when booting a crucial goal in the third quarter.

Higgins had his right knee examined by the doctors but managed to return to the field, albeit with his knee heavily strapped.

"They just described it as a contusion, which is another word for a bruise. But there's nothing serious or structurally wrong," Scott said.

Scott also said he had full faith that Todd Goldstein would deliver the go-ahead score deep in the final term but was not sure whether his set-shot kick at goal was the right option in the circumstances.

A contentious free kick went the way of the North big man in a ruck contest and with one and a half minutes left in the game he lined up his set shot from 55m out with scores tied at 75-all.

Goldstein's set shot sailed wide, but far enough to give the Roos a one-point lead before Mason Wood sealed the seven-point win with a shot after the siren.

"We did have a discussion about that after the game. He thinks he always had the journey in him," Scott said.

"It's an interesting one because even the decision to have the shot when the scores are level (comes into the equation). You need a certain level of maturity to make a decision definitively about what you're going to do.

"Whether you're going to look for someone in a better position, take the shot, rush the behind, all those things.

"The bottom line is when you give the ball back with enough time for St Kilda to score then that was always a risk."

Scott said Petrie's 300-game milestone was a talking point among his players prior to the game.

"It definitely plays a motivating role but it's channeling that back into the team that's the challenge," Scott said.

"Drew's such a loved figure within our club. A lot's been spoken about him this week and the common theme coming through is what a genuine person he is.

"We pride ourselves at North Melbourne about being real and Drew personsifies that."