A shoulder injury to James Fisher-Harris has soured Penrith's hoodoo-snapping 26-18 defeat of bogey side Parramatta.
Friday night's win in Penrith marked the first time since 2021 the otherwise all-conquering Panthers had defeated their local rivals in an NRL regular-season game.
The Panthers were still not back to their triple-premiership winning best, bombing certain tries either side of the break and proving uncharacteristically leaky on their goal line in the first half.
But back-to-back tries midway through the second period turned a two-point half-time deficit into an eight-point lead and had the Panthers on their way to a maiden win of 2024.
The triple premiers face a nervous wait as Fisher-Harris prepares for scans. Ex-Panther Reagan Campbell-Gillard felled the talismanic Penrith prop in the first half and he did not come back after leaving 15 minutes before the half.
Fisher-Harris was unable to return to the sidelines to watch the remainder of the game, either. Lindsay Smith appears the likeliest candidate to start in the front row if Fisher-Harris needs to miss next week's grand final rematch against Brisbane.
The Eels lost winger Bailey Simonsson to concussion in the opening minutes and had to reconfigure their left edge, with bench back-rower Kelma Tuilagi forced to play out of position at centre.
The reshuffle gave Penrith an outlet to attack from long range.
Their first two tries came thanks to Izack Tago breaks down the right, with Tago's outside man Sunia Turuva grabbing their third.
But twice in the first half, the Panthers misfired the final pass before they could turn other line breaks into tries.
Brian To'o and Liam Henry each spilt the ball at close range to bomb two certain tries either side of the break. Dylan Brown was the Eels' most effective player with the footy.
The five-eighth reignited his combination with Shaun Lane that found so much success in 2022 with a short ball that put the rangy back-rower over for the Eels' second try.
The Eels had an unlikely 18-16 half-time lead when Brown sent a flat pass to J'maine Hopgood at close range.
But after the break, as Tuilagi went down injured in backplay, Isaah Yeo fired a pinpoint perfect kick to Turuva for his second try of the night.
In Penrith's next set, Tago - immense with 255 metres - skipped through the defence as the Panthers finally appeared at their clinical best with the ball.
In the second half, Tuilagi appeared to injure his ribs attempting a big shot on Liam Martin, forcing Bryce Cartwright to become the Eels' third left centre for the night.
With Maika Sivo still suspended, the Eels will likely need to call on Haze Dunster to play wing against Manly next weekend as concussion protocols rule Simonsson out.