McMahon had his first taste of Japan with the Wallabies this week, ahead of beginning a two-year deal in the Top League next season.
The former Rebels back-row has been in super form for the Wallabies in the past month and was again effective against Japan in Yokohama on Saturday.
The 23-year-old, who is expecting his first son with wife Nia in April next year, will play in Japan for the 2018/19 and 2019/20 seasons, which covers the 2019 Rugby World Cup, initially seeming to rule out his chance of involvement in the marquee tournament.
His stance on the 2019 Rugby World Cup has softened markedly since the news initially broke that he was heading to Japan, first ruling out playing in the tournament, but now keeping his options open.
The critical element of McMahon’s contract is that the second season is in his favour, so he could theoretically wrap up in Japan in 2019 and sign in Super Rugby for 2020, making him eligible for the World Cup.
That would be a similar move to that made by Kane Douglas in 2015, when the lock was granted an early release from his Leinster contract to sign with the Reds for 2016 and was immediately eligible for the World Cup.
There have also been reports that the Top League season will look dramatically different around the World Cup, which could affect McMahon’s moves.
“It’s definitely exciting to have the chance to be coming over here (to Japan) and experiencing that,” McMahon told the Australian Rugby Union’s official website after the Wallabies’ 63-30 win over Japan.
“It pops into my mind (that I won’t be part of it) but I’ve made the decision that I’ve made and I’m mainly focusing on 2018 and nothing beyond that.
“I haven’t shut the door on anything and if the opportunity is there and the club that I’ve signed with and the ARU talk then we’ll see what happens but I’m focusing on this tour and the next three games.”
Whatever happens beyond this year, McMahon wants to make the most of his final three Tests for now, pleased with a first-up win on tour.
“I’m super keen to make the most of it and if I keep getting the opportunity to play in the gold I’ll be taking it with both hands,” he said.
“Just the way you see the team continuing to build and the way it’s going and players step up like Hodgey (Reece Hodge) who really had a proper crack and Fang (Nick Phipps) getting a starting opportunity, it’s what you want.”
McMahon said the Wallabies would need to tighten up against Wales, with a few too many passes missing their targets in Japan.
“We threw in a few too many offloads when we needed to keep building, (like) on that first try when we were just going up through the middle,” he added.
“Over in the UK they have a very forward pack mentality so we’re going to have to step up there and get very physical with our carries. We’ve got a focus this week in making sure that we’re first there both on our carry and our clean outs.”
Japan’s breakdown players got the better of the Wallabies at times as well and that’s something McMahon said they would need to work on their speed at the ruck.
“They were a very dynamic side and they were getting there very quickly and our timing was probably half a second too slow on one or two of our carries where it was crucial for us to be there,” he said.
“We missed it by half a second and that’s where they came away with those two or three penalties where they were over the ball.”
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