Harper put up his hand and took full responsibility for the Jets' opening round performance, where they lost to The Rock-Yerong Creek in the grand final rematch by 67 points.

It doesn't get much easier for the Jets as they prepare to take on Marrar at Ardlethan Sportsground on Saturday. The Bombers opened the season in style with a big win over Temora last Saturday.

After going into round one on the back of just one trial game, Harper said it was his fault the Jets were found to be off the pace.

"I can take a full responsibility for how we played on the weekend, to be honest with you," Harper said.

" I think we were slightly underdone, I think we were maybe not 100 per cent ready.

"I think for that first quarter especially, we were a little bit off the pace nearly all over the ground but as the game went on, we started to find our groove a bit and started to play footy a little bit more on our terms and we moved the footy how we wanted to, especially in the fourth quarter.

"As disappointing as it is to lose by 10 goals or whatever it was round one to the reigning premiers, there was plenty of positive signs to come out of it as well and things that are really easy to fix.

"It was a bit of a slap in the face but it's probably good to get it out of the way now rather than the end of the year."

The carnage wasn't just on the scoreboard as the Jets finished with just one fit player on the interchange bench.

The Jets cited TRYC's Shannon Williams this week for an alleged bump that left Ryan Cox concussed. The case was dismissed by AFL NSW-ACT on Wednesday due to insufficient evidence.

Cox won't play on Saturday due to concussion but Harper revealed assistant coach Sam Fisher is some chance after pulling up well from a heavy knock that saw him play no further part in the game.

Harper did not rule him out of playing against Marrar.

"We're unsure uet. He might get passed by the doctor and be able to return," he said.

"I doubt he will play on the weekend but he might still be half a chance."

With Cox out and Fisher unlikely, Harry Roscarel, Tom Roscarel and Henry Grinter will all push for selection after starting out in reserve grade last weekend.

Nate Doyle won't be back until after the Jets' round five bye due to badly broken finger sustained in their trial game, while Chris Bell is still 'a week or two' away as he gets his body right for the new season.

Harper wants to see the Jets play with a lot more fire against the Bombers on Saturday.

"Marrar are a quality outfit that have added plenty of spark to their list this year as well," he said.

"I think coming off the back of a pretty good win round one, they're going to be up and about but we still see ourselves as a team that can stick it to anyone.

"I think we just change the way we started the game, play with a bit more mongrel and a bit more fight and it should be a really good hit-out again this weekend and we'll continue that rivalry with them."

The Jets expect to keep Charlie McCormack for another week with him not required for VFL duties with Greater Western Sydney (GWS).