Armstrong was speaking on Tuesday in the aftermath of the Devils' 14-point loss to the Sydney Swans Academy on Sunday in Blacktown, where they came from 26 behind at three-quarter time to cut the margin to nine.

"I think we were a little bit underdone to be frankly honest,'' Armstrong said.

"This is the first time these guys are going to be playing, hopefully, 17 or 18 games, at that level, so we deliberately held them back a little in the practice matches, so they were a little bit underdone. But give them a week or two they should be hitting their straps."

Armstrong said the Devils were still learning the game plan of coach Adrian Fletcher, but noted they looked better as the game went on.

There will be no period of relaxation, with Armstrong saying they were taking every game seriously with spots in the Allies team for the national championships up for grabs.

"They are learning week-by-week, what Fletcher's structures as we haven't had a lot of games to put those structures in place. 

"(He is a) very defensive coach, with a mindset to set up from attack.

"It will be like any competition, there will be strong sides and weak sides, but on a weekly basis, coming up week-after-week when normally you'd play four or five games and have a spell within that, is going to be a challenge for our boys.

"At that level, sustaining those intensity levels week in week that is going to be the challenge."

 Armstrong also noted that seeing fellow Tasmanians (Chayce Jones, Tarryn Thomas and Jay Lockhart) make their AFL debuts in the first two rounds of this year had been a confidence booster for the group.

The Devils will continue their NAB League campaign against the Northern Territory at Melbourne's Holden Centre on Sunday at 1pm, before playing the Calder Cannons at Penguin on April 14.