Penrith Panthers forwards James Tamou and Viliame Kikau have defended coach Anthony Griffin's controversial decision to play the first half of their final trial without an interchange as short-term pain for long-term gain.

They started brightly against a reserve-grade Canterbury-Bankstown Bulldogs line-up before falling away badly towards the end of the first half, then produced a sluggish second 40 minutes to fall to a 24-10 loss.

Tamou and Kikau said they were forewarned about the long stint in hot, humid conditions and the boost in match fitness would pay off when the team faces a heavily fancied Parramatta Eels outfit at Penrith on Sunday.

"I think it was more getting the lungs working," Tamou told NRL.com.

"We spoke about it and we had a tough pre-season and wanted to really test ourselves. It's a whole different ball game that match fitness. You can run around the [training] field all day but when you get to that match fitness it really tests you and we'll only be better for it.

"We wanted to try and test ourselves and we really tested ourselves."

Panthers v Eels

Tamou admitted the team was "a bit blown away" when the Bulldogs started bringing fresh forwards on against the tiring Penrith middles late in the first half.

"We've got the work-out in and we'll be prepared for round one rather than not be," he added.

He shared five-eighth James Maloney's view that the Dogs' fringe players had more to play for in that trial, while it was tougher for Penrith to find motivation against an understrength team.

"We were playing a team that had a reason to play. And take nothing away, they played unreal, some of their big boys have really good footwork and we couldn't contain them."

Young back-rower Viliame Kikau admitted he was struggling late in the half. Although he got some big minutes for Fiji in the 2017 World Cup as a back-rower he is unaccustomed to long spells at NRL level having come through from the under 20s as a prop.

Panthers forward Viliame Kikau.

"I was blowing, and I was on the edge – I can't imagine the boys playing in the middle!" Kikau laughed.

"They were trying to see how we were going to go at the back end when the fatigue kicks in and how we communicate when we're defending."

Aside from an energetic pack bolstered by former Roosters giant Kane Evans and freshly re-signed lock Nathan Brown, the Eels would also profit from the return of prodigal son Jarryd Hayne – a man Tamou knows well from several years in NSW Origin camps together.

"In a way I think he's a bit more comfortable. You always are where you first start off," Tamou said.

"He's got something to prove and I don't think it will take much for him to show that. We all know he's an exceptional talent. Big, fast, can score a try anywhere on the field. You add Bevan French and Corey Norman into that mix, it's going to be tough."