A try-scoring double from Pumas winger Ramiro Moyano did the damage as the Waratahs slumped to their eighth defeat of the season at Bankwest Stadium on Saturday night.

Semi-finalists last year, the Waratahs now trail the Brumbies by eight points in the race for Australian conference honours with just three rounds remaining.

Even if they beat the Melbourne Rebels on Friday night, then the Brumbies in the penultimate round, the Tahs would likely need an improbable slip-up from the Brumbies against the bottom-placed Sunwolves next week to have any faint hope of making the play-offs.

"It's going to be very difficult from here on in," said Waratahs coach Daryl Gibson.

"In terms off those three games, we're very much still wanting to play the rugby that we've set out to play all year. That hasn't changed for us.

"I know guys will turn up and keep fighting, keep answering the call, and that's what I expect.

"We've got a lot of pride in or team and a lot of pride in our jersey, so there's plenty to play for."

On their latest lacklustre display, the Waratahs would only be making up the numbers in the finals anyway.

While once again gritty, Gibson's side lack the firepower and polish to seriously contend for silverware in 2019.

They weren't helped at all by losing star centre and Wallabies World Cup hopeful Karmichael Hunt in the second minute to a knee injury.

"Karmichael looks like he's got a grade three medial strain, so that's definitely season ending," Gibson said.

Hunt's departure further robbed the Tahs of another attacking strike weapon, something Gibson could ill-afford having already lost try-scoring whiz Israel Folau following the termination of his contract last week.

Starved of possession, the Waratahs' only first-half points came from a 36th-minute penalty goal to Bernard Foley as the Jaguares took a 10-3 lead to the break courtesy of Moyano's first try, which Domingo Miotti converted before adding a penalty.

The Waratahs looked shot ducks when Moyano crossed again eight minutes into the second half to extend the Jaguares' lead to 17-3.

But with their season on the line, the desperate hosts mounted a fightback, pulling to within seven points after being awarded a penalty try in the 55th minute following a dominant maul from a 5m lineout win.

NSW fans thought their side had drawn level shortly after, only for Nick Phipps to be denied a try when the television match official spotted Curtis Rona placing his foot in touch before getting a pass away in the lead-up.

Rona, though, atoned when he dived over in the left corner with 15 minutes remaining.

Alas, Foley's conversion attempt from the sideline ricocheted off the left upright, leaving the Waratahs still trailing by two points.

Two late penalty goals, including one after the fulltime siren, denied the Waratahs a precious bonus point.

Australian Associated Press