But after being named as one of the bolters in the 31-man Wallabies World Cup squad in Sydney last Friday, he has every intention of trying to make up for any lost game time in the coming weeks.

When Wallabies coach Michael Cheika named the 21 year-old as one of his out-of-the-box selections for the World Cup in Britain, he spoke glowingly of the Brisbane-born player's sheer energy at training.

Cheika recalled how anyone who has trained with McMahon knows it afterwards - in body and soul.

And Cheika's right. The same could be said of anyone who has watched McMahon train. His bloodied head wrapped in red bandages after a recent Wallabies session in Sydney remains a stand-out image.

Asked if his unbridled intensity at training was something he has brought from the day he made his debut in the Wallabies squad last year when he earned his three caps on the Spring tour, McMahon didn't baulk.

"Being a young player I was going there to learn from the older experienced players," McMahon replied.

"But I knew that I had to bring something that no-one else had.

"So I had to bring that intensity to training … go as hard as I can because if I wasn't going  to get game time that is where I had to leave my imprint on the field … there at training."

Pressed on whether he had doubted that he would make the World Cup squad because he had not played any Test rugby this year, McMahon said: "[It was] not so much that my chance had gone.

"In the back of your head, as a lot of players were probably in the same place as me, were second guessing themselves …

"I was just out there training hard and if my opportunity came I was going to take it with both hands and luckily enough it has.

"And I am going to take it with both hands and do the best I can.

"I have higher aspirations. Everyone here does. Everyone wants to be going over there [to the World Cup in Britain] to play footy and that's me as well.

"I will be going in there to training with the intent that I could be getting an opportunity out on that field to have a dig

"With the experienced players around me giving me knowledge and tips, basically building my game, it's definitely possible."

With Michael Hooper and David Pocock being world class No. 7s and Pocock a strong No. 8 option, McMahon rates his best chances of Test time at the World Cup as being cover for No. 6 where Scott Fardy is a premier pick, or at No. 8 where Wycliff Palu and Ben McCalman figure strongly.

"I can play most positions in the back row, but I think my best chance is that six or eight role, trying to cover there," McMahon said.