Gordon fell to the ground in agony after attacking the line late in Sunday's (AEST) 28-28 draw with Argentina in Mendoza.
The side doesn't land back in Australia until Monday night but it's understood scans post-game revealed the 25-year-old had suffered a leg fracture that will keep him sidelined for two months.
That injury would rule him out of the Wallabies' Perth Test against the Springboks on September 26, as well as next month's two-Test Bledisloe Cup series.
There is hope he would be fit in time to face England at Twickenham on November 8.
It's the latest injury blow for the luckless playmaker, who suffered a serious back injury that derailed his NRL cameo and has battled various leg niggles since returning to rugby barely a year ago.
Ben Donaldson started in that position against Los Pumas for the first time in two years, but Gordon had established himself as the first-choice playmaker under Kiss.
Donaldson failed to put his stamp on the contest and will now face stiff opposition to retain the jersey, with fit-again Reds flyhalf Tom Lynagh likely to return from a long injury absence of his own in Super Rugby Aust, on Saturday against the Western Force.
Declan Meredith started in three Tests this year and was in the Argentinian tour squad, while Harry McLaughlin-Phillips could also mount a case in new Force colours in the pre-season competition.
Test veterans James O'Connor (Force) and Bernard Foley (NSW Waratahs) will make Super Rugby Pacific returns next year and both harbour World Cup aspirations, but will not feature in Super Rugby Aust.
Australia's forwards have impressed during a five-game unbeaten streak but Gordon's injury, as well as the form of fullback Tom Wright and lack of impact from big-money centre Joseph-Aukuso Suaalii, mean question marks remain ahead of Kiss's biggest test yet.
"We know we've got to be better than what we were, but we can see the growth," said in-form halfback Ryan Lonergan, who finished the game acting as flyhalf because of Gordon's injury.
"If we get our game together on both sides of the ball ... tidy up our attack, we've got a chance of pushing them (the Springboks) a long way.
"Joe (former coach Joe Schmidt) gave us a great platform to play off and now, with the continuity in the team and little changes and tweaks Les has brought into our attack, the ceiling for our attack has lifted and we look like we have more points in us.
"Now it's about converting it."
Missing a host of overseas-based stars, Los Pumas exposed Australia aerially and the visitors struggled to exit their danger-zone with any authority in what Kiss described as an enlightening fact-finding mission.
"Some of the decisions we've made over this four, five weeks, we got a lot of information from it," he said when asked how he'd approach selections for the next phase of matches.
"It'll narrow the mindset about how we go forward.
"It was important this group knew we'd back them, challenge them in many different ways and we'll get a lot of pay for that down the road.
"We're playing the No.1 nation in the world. What are we, seven or six? So we need to get some things better. But the boys will be up for the fight."
