Pat Richards kicked the penalty to lock the scores up at 16-16, and three minutes later the winger's magic boot landed arguably the field goal of the season.
After a flurry of desperate last-tackle passes, the Tigers continued to lose ground, before Richards found himself with the ball for the second time in the movement and snapped a field goal from 32 metres out, near the left touchline.
The Knights' woes continued to snowball when prop Kade Snowden found himself on report for the second time in the match, and off the back of that, Chris Lawrence scored and Richards converted from out wide to put the visitors in front by seven.
When Gidley returned to the field, Akuila Uate crossed for his third try of the match with three minutes on the clock to give the Knights a glimmer of hope.
But after deciding to knock back a shot at goal, the Knights weren't able to break up field and set themselves up for a miracle finish - and the Tigers secured their place in the top eight.
There were two silver linings for Newcastle, with Uate breaking the Knights' all-time try-scorer's record and much-maligned Newcastle fullback Darius Boyd once again showing his big-moment ability.
In his 200th NRL game and with Queensland's backline dealing with an injury crisis ahead of State of Origin II, Boyd produced a masterclass at fullback for Newcastle to ease headaches for Maroons selectors.
Boyd has scored 14 tries at Origin level in 18 matches on the wing, but is ready to step up and wear the No.1 shirt for Queensland should Billy Slater (shoulder) and Greg Inglis (ankle) fail to recover in time for the must-win ANZ Stadium clash.
Knights coach Wayne Bennett decided to switch his wingers Uate and James McManus before the game - allowing McManus to audition for the vacant NSW spot on the right.
Tigers five-eighth Braith Anasta was forced off the field with a concussion problem in the first half, after he landed on his head attempting to catch a bomb in his own in-goal.
Anasta clipped teammate Tedesco on his jump, with Newcastle's Tyrone Roberts touching down on the spilled ball for a try.
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-AAP