The Jaguares played so badly for Pumas coach Daniel Hourcade that he resigned this month.
As Pumas, they lost all three home tests, abysmally. But back under Mario Ledesma's care in Super Rugby, the Jaguares were on Saturday everything they weren't as Pumas: composed, smart, and lethal.
They handled the visiting Stormers 25-14 to beat the South African side for the first time, and rack up a seventh straight win, including six before the month-long international break.
After losing five of their first seven matches, it has been a remarkable turnaround by the Argentine outfit.
Matias Orlando scored 51 seconds into the second half to stretch the advantage and Stormers never looked like succeeding on the road for the first time this season.
Jaguares are three points behind leaders Lions in the South African conference, but have two regular-season matches to play and the Johannesburg outfit only one.
Elsewhere, the Chiefs scored six tries and 42 unanswered points in the first half of a compelling performance against the Highlanders. The Chiefs' first-half blitz allowed them to ease off in the second for a 45-22 win over their New Zealand rivals in the Fiji capital Suva.
The match was thought likely to be close between teams separated by only three points in the New Zealand conference; the Dunedin-based Highlanders in third place and the Hamilton-based Chiefs just behind in fourth.
It was a complete blowout in the first 40.
In South Africa, the Sharks beat conference leaders the Lions 31-24 with a second-half surge that saw the home team come back from 21-11 down at half-time.
The crucial moment came when Sharks winger Lwazi Mvovo scored off an intercept to put the Sharks ahead with 10 minutes to go.
The Sharks' victory ended three years of dominance by the Lions over their fellow South African teams in Super Rugby. The Lions' last loss against a South African outfit was in 2015.
Playing at their second home in Singapore, the Tokyo-based Sunwolves beat three-time Super Rugby champions the Bulls of South Africa 42-37. The Sunwolves sealed victory in a match that swung back and forth with Rahboni Warren-Vosayaco's 75th-minute try.
It was one of six tries for the Sunwolves, all converted by flyhalf Hayden Parker, who also scored the first try.
It was also only the third win of the season for the Sunwolves.
Of the Jaguares line-up, 14 started for Argentina against Wales on June 9 and were crushed 23-10. The lineup changed little in a second loss to Wales and a thrashing from Scotland last weekend.
But against the Stormers, tries to winger Bautista Delguy and lock Guido Petti in the first 15 minutes for 15-0 gave the Jaguares control they never looked like relinquishing.
The Jaguares are threatening the Lions for the South African conference lead, and play the last two rounds in the republic.
The Chiefs' stunning first-half show against the Highlanders included two tries to winger Tony Pulu. The result might be pivotal in Super Rugby's wild-card playoff race.
The Chiefs, playing with a powerful wind at their backs, dominated the Highlanders with three tries in the first 15 minutes, another that made it 28-0 after 25 minutes and two more tries in one of the most one-sided halves seen in a New Zealand conference match.
The Highlanders weren't able to compete, even to get their hands on the ball. They did rally strongly with four tries in the second half, including a late try to new All Blacks flanker Shannon Frizell, which denied the Chiefs a valuable bonus point.
"That was a classic example of how to play with the wind," Chiefs captain Sam Cane said. "We got it spot on in the first half but the Highlanders played pretty sharp with it in the second half so we feel glad we got enough points in the first half to hold on."
In the Australian capital Canberra, the ACT Brumbies held the Wellington-based Hurricanes scoreless in the second half for a 24-12 win, the Brumbies' first win over a New Zealand team since 2016.
The Hurricanes, who went to Canberra without stars Beauden Barrett, Vaea Fifita, Ardie Savea and Brad Shields, took a 12-5 lead into the break through a try from Julian Savea.
But the Brumbies took the lead early in the second half with tries to hooker Folau Fainga'a and lock Rory Arnold.
Fainga'a's effort made the Brumbies the first Australian team to reach 1,000 Super Rugby tries and third in competition history behind the Hurricanes and Crusaders.
The Hurricanes remained in second place in the New Zealand conference, nine points behind the leading Crusaders, who had a weekend bye.