Tru Plant Tigers succumbed to a third home defeat of the campaign with the away side producing a classy second-half display to notch a seventh successive victory.
Scores were level after seven races before a Panthers maximum courtesy of former World Cup winning duo Hans Andersen and Bjarne Pedersen in Heat 8 proved to be the catalyst to a run of six race victories out of eight.
British champion Ellis tallied up 12+1 with number one Jack Holder scoring 10+1 - contributing three out of the five Tigers heat winners between them on the night.
Middle order pairing Kyle Howarth and Josh Pickering each added six points with rising star Danyon Hume getting the better of former Grand Prix star Andersen to win his opening ride.
Despite the defeat, the Owlerton faithful were treated to a series of spectacular races including a contender for ride of the season by GB legend Chris Harris.
“They were definitely the better team,” said Ellis. “We weren’t on great form tonight and they’ve come here and made the most of it - they’re a really strong team all the way through.
“We’ve been a bit unlucky with injuries but it’s tough to take, especially at home just before the play-offs.
“Hopefully when we get back here next week we can put things right.”
Simon Stead’s team head to Peterborough for their final regular away league fixture of the season on Monday (September 20) before returning home on Sunday (September 26, 5pm) for the visit of bottom club King’s Lynn.
SHEFFIELD 40: Adam Ellis 12+1, Jack Holder 10+1, Josh Pickering 6+1, Kyle Howarth 6, Danyon Hume 3, Troy Batchelor 2+1, James Wright 1.
PETERBOROUGH 50: Chris Harris 13, Michael Palm Toft 9+1, Bjarne Pedersen 8+1, Connor Mountain 8+1, Hans Andersen 6+1, Thomas Jorgensen 4, Scott Nicholls 2.