Sean McMahon has mark of a future star as he prepares for Wallabies Test debut Sean McMahon trains with the Wallabies this week. NEWEST Wallaby Sean McMahon would give his right arm for his family. He's already given his left for his Grandma Betty. Tattooed on his left arm is the word McMahon. His father Pat and two brothers Adam and Sam have the same tattoo. "We all got together and had it done for my Gran's 70th birthday," he explained. We surprised her. She didn't like it at first, but then she loved it. McMahon, at 20 the youngest Wallaby on tour and the only newcomer in the side to play the Sunday morning (AEDT) Test against Wales, is a rugged, raw, bundle of muscle and enthusiasm who shows a softer side when talking about his parents and brothers. Contacting his father Pat, who is a FIFO security specialist working in West Africa for three-month stints, and mother Shauna back home in Brisbane, to tell them of his selection was one of the greatest moments of his life. "Mum was asleep when I found out but I could text Dad in West Africa because the time is about the same," McMahon said. He was stoked. He texted back, "Mate I'm absolutely speechless. I don't have the words. I'm so proud of you. You deserve it. I rang Mum when she woke up. She was pretty emotional. To be able to tell your mum and dad something like that, it melts your heart. Sean McMahon, right, shares a joke during a Wallabies training session in Cardiff. Pat and McMahon's second eldest brother Sam were due to fly into Cardiff on Friday to watch the match, making the occasion even more unforgettable for the young backrower who began the 2014 season with the Melbourne Rebels not giving himself a chance to make the Wallaby squad, let alone the Test side. "At 20 years of age with so many great players ahead of me I thought I was a long way down there," he said. This whole thing is mind-blowing to be honest. But while McMahon might be in a state of disbelief, Wallaby coach Michael Cheika said he had little choice but to pick him after his blockbusting performance against the Barbarians last weekend. "He got an opportunity and he took it," Cheika said. He wasn't scared to carry the ball or get involved and be aggressive; to run hard, tackle hard. I think all this talk of it being a great way to cap the year for him is wrong. I think it's the start for him. He's got an opportunity to really build something going forward. It's been enjoyable to coach him so far. He'll bring what he brings as part of his profile and it's becoming clear that he's a tough guy who likes to get in the mix and get involved. He wants to be part of it. He wants to take responsibility and make something happen, not just sit back and watch it unfold. Sean McMahon starred for the Wallabies against the Barbarians. All those elements of toughness, aggression and physicality were on show against the Barbarians and will no doubt light up Millennium Stadium this weekend, although one only has to ask about the importance of family, to see his other side. Mum putting in countless hours to get me to rugby and dad working overseas to give me opportunities like going to Nudgee College ... family is a big thing for me. Having dad say I'm flying me and your brother over for your debut is just huge. Grandma Betty's tattoo isn't McMahon's only body ink. On his right forearm are the words, "Life is what you make of it." There is another tattoo hidden somewhere, the words and position of which he says through laughter "better remain personal," and a full back piece consisting of two angels holding each other. Across the top is the McMahon family motto: What We Have We Hold, and underneath, four names that make it clear that Australia's latest Wallaby is a key member of another team as well. Pat. Shauna. Adam. Sam.