The 32-year-old, who is shifting his career from France to Japan, is primed to make his first appearance of the year for the Wallabies as they look to rebound from a disappointing home series loss to England.
Arnold has replaced Samu Kerevi as one of coach Dave Rennie's three overseas-based player picks, with the blockbusting centre joining the Sevens team at the Commonwealth Games in Birmingham.
Ex-Brumby Arnold said he picked up a calf injury while trying to keep fit following the end of the French season six weeks ago.
"I've been on holiday ever since and I was just doing a bit of extras and felt a bit of a calf strain so last week I was rehabbing that and she's coming good now so good to go," Arnold said on Thursday.
He admitted he could be a little off the pace set by players who were part of the three England Tests but felt he could make up ground before the match in Mendoza on August 7 (AEST).
Arnold is vying with Matt Philip, Nick Frost, Jed Holloway, Darcy Swain and Rob Leota for a second row spot.
"Coming off the England series they're going to be fit and ready to go and I'm probably a few steps behind them but I'm confident in my ability and I'll get up to scratch in no time," he said.
Apart from a call-up from Rennie for last year's UK spring tour Arnold played the remainder of his 29 Tests under Michael Cheika, who now coaches Argentina.
Arnold said he knew what to expect from a Cheika-coached side.
"It's good to come up against him and that group are obviously coming off some success with the series win over Scotland.
"All the teams that are coached by Cheik, he wants them to be physical and we will be expecting that next weekend against the Pumas."
Having played with European heavyweights Toulouse since 2019, Arnold hoped his experience could make a difference to the Wallabies pack.
"I've got a bit of experience now and I've played in some big games overseas," said the 208cm Arnold.
"I will just try to bring that calm sort of edge about it, and we'll see how we go."
While he has yet to disclose which club he will play for in Japan after signing a big money multi-year deal, Arnold said he hadn't ruled out a return to Australian rugby.
But he supported the Giteau Law, which limited the number of overseas-based players who could be selected into the Wallabies.
"You can see why it's there, to keep the talent in Australia and playing Super Rugby ... there's tough decisions to be made."
Meanwhile, veteran prop Scott Sio has withdrawn from the two-Test tour after failing to recover from a shoulder injury suffered in the second England Test.
Western Force front-rower Tom Robertson has joined the squad as his replacement.
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