After being presented with his jersey the day before by Knights 1997 premiership star Darren Albert, the 23-year-old went out and played with Albert's game sense.
The Dolphins' afternoon at Suncorp Stadium grew worse when captain Jesse Bromwich left the field in the second half with a calf injury.
Newcastle also lost forward Jacob Saifiti to a lower leg injury.
Armstrong and Dolphins pocket dynamo Trai Fuller, in just his third NRL game, had a classic No.1 battle and were two of the best players on the field.
Try-scorer Tyson Gamble and the Knights were overjoyed to beat the Dolphins on their home turf. (Jason O'BRIEN/AAP PHOTOS)
Armstrong scored the opening try and made a try-saving tackle on Fuller in the second half. He was magnificent under the high ball and in general play with his elusive running.
Ponga is set to miss 12 weeks with a Lisfranc injury to his foot but Armstrong showed coach Adam O'Brien he was more than ready to play at the top level.
"He is a little bit uncanny. Stuff happens around Davey. We had Darren Albert present his jersey and we spoke about how stuff happens around Alby," O'Brien said, highlighting similarities between Armstrong's try and Albert's in the 1997 decider.
"With that try, Davey was just pushing up on the inside of players. It is pretty fitting we got Alby to present that jersey to Davey. He has that ability.
"We just needed to come here and find a way to win. We spoke a lot about the DNA of our town and club.
"We want to be tough and gritty and we thought we had fallen out of love with that part of the game, chasing the flash stuff. Today was a step back in the right direction."
Fuller was electric and brave but his teammates struggled to get out of second gear until it was too late.
"We played pretty flat all day actually," Dolphins coach Wayne Bennett said.
"We expected to come here and play well and to their credit they stayed at it and didn't give up."
Oryn Keeley crossed for the Dolphins but it was the Jets who were airborne on Sunday. (Jason O'BRIEN/AAP PHOTOS)
Knights props Leo Thompson and Jacob Saifiti, in his 150th NRL game for the club, ripped in early to set up a 10-0 lead as a sluggish Dolphins outfit bumbled their way through the opening quarter of the match.
The visitors were rewarded for their discipline and patience when half Jackson Hastings threw a sublime inside ball to Armstrong, who sliced over untouched.
Five-eighth Tyson Gamble found veteran Dane Gagai with a slick pass and the centre showed his experience to hit a hole and score.
The Dolphins didn't get out of first gear until centre Jake Averillo blitzed opposite number Bradman Best and found second-rower Oryn Keeley, who scored his first NRL try against his former club.
Dolphins forward Kenny Bromwich failed a category two HIA and Knights forward Jed Cartwright was ruled out with an ankle injury, both in the first half.
Gagai waltzed over after the break thanks to pathetic defence as the Dolphins allowed bench hooker Phoenix Crossland to burst into the clear.
The Dolphins bombed two tries, one when Averillo failed to collect a grubber kick through by Kodi Nikorima.
Nikorima set up Jamayne Isaako for a try and Averillo finished a classy movement, both in the last five minutes, but it was too little and too late.
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