Injury-ravaged Melbourne have blown the chance to wrap up their third successive NRL minor premiership with Penrith winning a 22-16 arm wrestle at AAMI Park.
The Storm loss opened the door for the Sydney Roosters to claim the JJ Giltinan Shield, they need to beat last-placed Parramatta on Saturday night and make up a 27 point differential to move ahead of Melbourne on the ladder.
Melbourne skipper Cameron Smith said it was disappointing to let the opportunity slip.
"We are all very disappointed with result because if we'd won we would have wrapped up the minor premiership and now we have to wait on results," Smith said.
"Either way we're guaranteed top two - winning the minor premiership would have been really nice but if finish second it will be the same scenario for us and we will have a home final."
Penrith winger Josh Mansour scored a try in each half while centre Waqa Blake also collected a double, with the win snapping their two-game losing streak.
Panthers interim coach Cameron Ciraldo said he "couldn't be prouder".
"It's been a tough couple of weeks ... the way they hung in their tonight I couldn't be prouder of their effort," Ciraldo said.
The Storm were drastically undermanned, with halves Cameron Munster and Brodie Croft late scratchings with knee injuries to join an already bulging casualty ward.
They were already without Billy Slater who remained in North Queensland on personal leave so promising youngster Scott Drinkwater was handed a NRL debut at fullback.
Drinkwater looked right at home with some exciting runs and was rewarded with a late try that could prove crucial in the minor premiership mathematical equation.
The Storm led 10-6 at halftime after a bizarre opening 40 minutes that saw Penrith's both Mansour and James Tamou sinbinned with the visitors hammered 11-4 in the penalty count by referee Gerard Sutton.
Mansour was given time out for pulling on the arm of Storm winger Justin Olam as he tried to score while Tamou was pinged after repeated infringements by his team.
In Mansour's absence Storm second-rower Felise Kaufusi dummied and then barged through the defence, with the conversion giving his team a 8-4 lead.
Melbourne blew three tries with Olam twice going into touch as he attempted to ground the ball while Drinkwater's effort was ruled no try due to obstruction.
Mansour's second six minutes into the second half levelled the score at 10-10 as the Panthers, who had never before won at AAMI Park, started to dominate.
The scoreboard kept ticking over through Blake's two tries and then winger Christian Crichton, who showed his speed in a 60 metre dash to the line.
Drinkwater gave his team a sniff with his 75th minute try and they threw everything at Penrith but couldn't come up the match-winner.