NORTH Melbourne's focus against Port Adelaide on Friday night will be on arresting an alarming capacity to leak scores from centre bounces.

Coach Brad Scott said the Roos, on one win and four losses after their disappointing 58-point thumping by Essendon on Good Friday, have been concentrating heavily on their centre-square work this week.

"We had a really good session during the week, it's our first seven-day break in a while so we got an opportunity to put some quality work into the players, and physically they're in better condition," Scott told reporters on Thursday.

WHO MAKES FINALS? Do the 2019 Ladder Predictor

"Mentally, it's been a challenge. Clearly, at 1-4, the challenge is to focus on what's important and not get distracted by the frustrations we're experiencing.

"The main one, to be honest, is how do we address conceding 130 points from centre bounces (across five rounds).

There's been changes to the centre-bounce system, and we've talked about how we're a little bit limited in how we can defend them, but the reality is, the second-worst team at defending centre bounces is conceding less than half of the score we have.

"That's not just centre-stoppage wins, it's the ability to defend them, and just we're not defending them well enough."

Scott forecast some different faces to be moved through the centre on Friday night, while also confirming defender Luke McDonald (suspension) and exciting youngster Tarryn Thomas (rested) would return after missing last week.

FREE AGENTS LIST Who is in this year's pool?

"We're making some changes because we have to. Trust me when I say I've been through every single one of them and analysed every other team in the competition as to why we're defending them poorly in comparison to the rest of the competition," Scott said.

"Part of it is credit to the competition – they've moved the ball well against us, but we haven't defended anywhere near well enough.

"We'll look different this week in the way we go about it, and we'll have to just keep chipping away at it. I've got no doubt that it will smooth out as the season goes on, but right at the moment, there's a lot of factors we're not doing anywhere near well enough, but that's the one that's costing us the most."

A lot of attention has been on captain Jack Ziebell and the amount of time he has spent up forward as opposed to in the middle of the ground.

MID-SEASON DRAFT 50 players who could spark up your list

Ziebell had just six disposals and three tackles last week against Essendon.

"One thing we've had is the option to put guys through [the centre square]. Our captain has spent a bit of time – contrary to popular opinion, apparently – he spent time in there on the weekend," Scott said.

"We'll make some changes to our forward half as well, which will then flow on to our midfield."