The Canterbury Cup Panthers overcame all odds to stun the ladder-leading Mounties 30-22 at Aubrey Keech Reserve on Sunday.
Kaide Ellis, Hame Sele, Jarome Luai and Tyrell Fuimaono were late scratchings from the side following a significant injury toll and judiciary drama arising from the Panthers' NRL defeat to Canberra on Saturday.
Shawn Blore (ankle), Spencer Leniu (knee) and Daine Laurie (concussion) were also ruled out before the game, forcing Panthers to call on St Marys representatives Allan Fitzgibbon, Kurt Falls, Meni Luke and George Tsikrikas.
In addition, youngsters Adam Fearnley and Brad Gaut backed up on the bench despite having played for the Panthers Jersey Flegg side in Wagga Wagga on Saturday.
But a Billy Burns double and composed performance from fill-in five-eighth Falls led the Panthers to a hard-fought win.
The undefeated Mounties, on the other hand, had plenty of experience to draw on in the form of halves pairing Ata Hingano and Aidan Sezer.
Early back-to-back penalties saw Mounties march upfield and quickly capitalise, Emre Guler crashing over next to the posts to hand the home side an early 6-0 lead.
Both sides were guilty of ill-discipline early but it was Mounties who proved better at taking their chances. Andre Niko scored in the 15th minute as Sezer swung it left to Hingano, who put the winger over in the corner.
Niko was almost over again soon when Sezer weaved his way through the Panthers defence but a forward pass was called.
It proved a crucial turning point, a penalty seeing Penrith reduce the deficit to six after a Dylan Edwards grubber sat up for Ratu Tuisese.
The Panthers then hit the lead in the 30th minute when Burns pounced on a loose ball off a crossfield kick. Edwards kicked both conversions from the sideline.
Falls then broke through the line but couldn’t link up with an unmarked Allan Fitzgibbon, his pass hitting the ground and the ball spilling out.
And Mounties made them pay, going down the left edge on the following set as Reubenn Rennie flicked it on the inside for Niko to fly over. The successful conversion saw the score line stand at 16-12 at the break.
HALF-TIME: Panthers 12 Mounties 16
Mounties carried their momentum into the second half, extending their lead to 10 when Tom Starling put Reuben Porter over off a crash ball.
In the absence of starting halves Laurie and Luai, Falls stepped up and was rewarded with a try when he chased his own bomb and picked up the scraps in the 53rd minute.
In a cruel blow for the Panthers, Matheson Johns was sin-binned with 23 minutes remaining.
Just as Johns came to return from his ten-minute spell, Mounties looked to have landed the finishing blow when Tony Satini soared over in the corner, only for the play to be ruled back for a forward pass.
Having had a similar call go against them in the first half, it was déjà vu for the home side as Penrith went on to score off the ensuing set, rewarded for their defensive effort without Johns.
Five-eighth falls added to his impressive performance with a well-weighted kick, which sat up for a determined Fitzgibbon.
Edwards nailed the conversion from the sideline to give the Panthers a 24-22 lead.
Burns then surged for his second try of the afternoon and Edwards knocked over a penalty goal, sealing a stunning win for Penrith.
FULL-TIME: Panthers 30 Mounties 22