But the Canberra Vikings have been warned to expect a fired-up Skelton who will be out for redemption for the Sydney Stars just days after being axed from the Wallabies squad.

Arnold will be the tallest player in Super Rugby next year when the 208-centimetre lock makes his debut for the Brumbies.

Skelton is 203 centimetres and 140 kilograms, making him the most feared player in the National Rugby Championship clash against the Vikings on Saturday.

But Arnold, who has shed 10 kilograms since joining the Brumbies, is refusing to back away from the physical contest in his first game in 12 months.

"The one thing I'm looking at when I get on is making an impact off the bench," Arnold said.

"It will take a bit of getting used to after having surgery on my left shoulder, but I'll be giving it 100 per cent.

"If you run at [Skelton], you'll sure know about it. I'm looking forward to the challenge, he's a Test lock and it will be good to have a crack."

The injury-depleted Vikings will have to withstand an onslaught from Skelton as he begins his bid to win back his place in the Wallabies squad.

Test coach Ewen McKenzie dropped Skelton to give him more game time in the NRC instead of sitting on the Wallabies bench.

It's bad news for Canberra as the team aims for its third consecutive win in the NRC.

Arnold is playing his first game after recovering from shoulder surgery and signing a Super Rugby contract with the Brumbies.

The 24-year-old has dropped to 120 kilograms and his 208-centimetre frame will make him easily the biggest player on the field.

But he admits he has plenty to learn after only starting rugby seriously three years ago.

Vikings coach Dan McKellar will inject lock duo Tom Staniforth and Arnold late in the game and said Canberra needed to take away Skelton's time and space to minimise his impact.

"[Arnold's] size is obvious, he's pretty athletic and skilful. He's naturally pretty aggressive, too," McKellar said.

"That's certainly got potential ... His role is all about physicality and being prepared to get stuck in. Rory's a different player to Will [Skelton].

"You'd like to think Rory's still a massive body and can have that physical presence. But he's new to the game and we have to continue to work with him.

"I'm sure Skelton's not happy about missing out on the Wallabies. We just have to deny him time and space to stop momentum."

The Vikings will play without Christian Lealiifano and Joseph Tomane, who have both been called up to Wallabies duties.

Isaac Thompson will step in at five-eighth to fill Lealiifano's boots while Rodney Iona will start in his first NRC match in the same week he signed a Super Rugby deal with the Brumbies.

NATIONAL RUGBY CHAMPIONSHIP ROUND FIVE

Saturday: Sydney Stars v Canberra Vikings at Leichhardt Oval at 2.30pm.