One of the keys to North's 10-2 finish to last year's home and away season was the way Drew Petrie, Lachlan Hansen (both 197cm) and Robbie Tarrant (196cm) teamed up in attack to stretch opposition defences.
In 12 consecutive games from round 13 last season, they averaged a combined 6.3 goals, 14.3 marks and 5.3 tackles a game.
But the tall trio's productivity has been noticeably down so far this season, their combined averages slipping to 4.7 goals, 13.3 marks and 2.7 tackles a game.
Ziebell told AFL.com.au on Wednesday Petrie, Hansen and Tarrant each had an alibi for their quiet starts to the season.
"We don't really help our forwards out with our delivery," Ziebell said.
"Drewy's been All Australian but I don't really think we've helped him out this year with our delivery, the same with 'Taz' and Lachie.
"We just need to be a little bit more direct and make sure we give them a chance by putting the ball to their advantage and not forcing them to try and outmuscle two blokes.
"If we can let them come up at the footy, I'm sure they'll start to look really dangerous again."
North's opening three losses have come after it led at half-time against Geelong (by 35 points) and the Sydney Swans (14 points), and trailed by just two points at the main break against Collingwood.
The Roos effectively lost all three games in the third term, having been outscored by a combined 38-144 in the 'premiership' quarter this season.
Ziebell said North was determined to eradicate the 10 to 15-minute fadeouts that had typified those losses.
"It's quite disappointing that against Sydney, Geelong and even Collingwood to an extent we've given our opposition 10 or 15 minutes to get a bit of a run on and kick a number of goals – you can't do that at AFL level," Ziebell said.
"I think that's been the difference in the three games we've played, they've been able to have that 10 or 15-minute period where the pressure is almost released a little bit and they can kick quick goals.
"If we can tighten that up we'll be a very difficult side to beat."
Ziebell said North's players were conscious of the need to play with greater intensity in the third quarter against the Swans, but had nonetheless allowed them to pile on six goals in just over nine minutes at the end of the term.
"It's not like we go to sleep at half-time and we come out and we're just not working or anything like that," Ziebell said.
"It's more just a couple of things we do throughout the course of those third quarters, lapses of concentration.
"It's just about making sure everyone's playing their role for the whole 120 minutes, that's the biggest thing."
Ziebell agreed with his coach Brad Scott's assessment this week that Roos skipper Andrew Swallow needs more support in the midfield.
"'Spitta' (Swallow) has been fantastic for a long time now. He's almost been doing that inside midfield role alone, with pinch hits from myself and 'Cunners' (Ben Cunnington) and 'Wellsy' (Daniel Wells)," Ziebell said.
"Our challenge is to be consistent and give him a chop out and make sure that he gets the support he needs, week in, week out."
Nick Bowen is a reporter with AFL Media. Follow him on Twitter: @AFL_Nick
