South Africa winger Ruan Combrinck will probably miss the rest of the 2016 Rugby Championship after suffering a leg injury during a 26-24 weekend loss in Argentina.
One of the few success stories in a struggling Springboks side this season, the 26-year-old was injured in the first half and X-rays revealed that he had a fractured fibula.
A South African Rugby spokesman said the back could be out of action until mid-October. The last Championship fixtures are on October 8.
Combrinck, who can also play full-back, debuted off the bench for the green and gold during a June home series against Ireland and quickly became a first choice.
He was a key figure in the Golden Lions team that reached the Super Rugby final for the first time this year, impressing with his powerful running, strong defending and ability to convert long-range goal kicks.
There are also concerns about the fitness of fly-half Elton Jantjies, who will have a groin injury scanned when the team returns to South Africa Monday.
After a largely outstanding Super Rugby campaign, Jantjies has disappointed at Test level in the absence of injured rivals Patrick Lambie and Handre Pollard.
Lambie started the season as first choice, but was concussed early in the first home Test against Ireland and has not played since.
Coach Allister Coetzee said the Springboks lost in north-western city Salta because the Pumas made better use of scoring chances.
"They used their opportunities better than we did," admitted the 53-year-old, who succeeded Heyneke Meyer this year as coach of the twice former world champions.
"We had enough chances to create scoreboard pressure, but did not take them. At Test level, you take your chances or you get punished.
"Some penalties were missed and we did not score tries when in a position to do so."
Jantjies and his replacement, veteran Morne Steyn, each missed two kicks at goal.
"Despite losing Ruan and Elton, we came back in the second half only to make crucial mistakes, I am disappointed by the many individual errors," Coetzee added.
"This defeat hurts. We must regroup and work hard to improve as a team to be ready for Australia in Brisbane."
South Africa face the struggling Wallabies on September 10 and world champions New Zealand a week later in Christchurch.
New Zealand top the table after two rounds with a maximum 10 points, South Africa and Argentina have five each and Australia none.