Needing a win to stay in the race for the NRL top four, Cronulla started slowly at Shark Park on Sunday before a Ronaldo Mulitalo hat-trick helped them power home.
The win means Cronulla can finish fourth if Brisbane lose to Melbourne on Thursday night and the Sharks upset Canterbury two days later.
Even in a worst-case scenario where the Sharks miss the top four, they would have a home final in the first week, with a top-six finish now completely secure.
But the bigger question will be Trindall's fitness, one fortnight after losing captain Cameron McInnes to a ruptured ACL.
Trindall damaged his ankle in the first half of Sunday's win and while the five-eighth hobbled on, he eventually left the field after 51 minutes and had ice applied.
"He wanted to keep playing, and we could have kept him playing. So I don't think it is too bad," Sharks coach Craig Fitzgibbon said.
"But we felt like with what's ahead, why are we doing that?
"We'll obviously clear up what it is. It's a lateral (sprain) by the looks of it, but we won't know until we get an MRI."Â
Cronulla have Dan Atkinson as a back-up half but would want their play-making duo of Trindall and Nicho Hynes on deck for the finals.
The other concern for Cronulla was fullback Will Kennedy being placed on report for a high shot on falling Newcastle half Jack Cogger.
Sunday's result made it eight straight losses for the Knights and capped a week in which coach Adam O'Brien agreed to exit at the end of the year.
Those interested in succeeding O'Brien will have seen positives in the opening 20 minutes as Newcastle raced to a 10-0 lead.
Fletcher Hunt scored from a Phoenix Crossland kick, and Bradman Best and Greg Marzhew showed the Knights' threat out wide for another try.
But that was where the positives ended for Newcastle, who were behind and gave away an offside penalty from a kick-off just 10 minutes later.
It leaves Newcastle potentially needing to beat Parramatta in the final game of the season next Sunday in order to avoid the wooden spoon.
"Once they got the first try it unravelled for us a bit," O'Brien said.
"Then the second half we didn't start with any level of intensity that is required. We were way off the pace."
Unsurprisingly it was Blayke Brailey's straight running out of dummy-half that put Cronulla back on track, sharpening their attack as the game swung.
Addin Fonua-Blake sent a reminder of why he can be the difference at Cronulla this year with a barge-over try, and Hynes sent Siosifa Talakai over before halftime.
Mulitalo, meanwhile, had a field day.
He scored his first on the end of a sweep play and Trindall cut-out ball, before adding to his tally from a lofted Kennedy pass in the second half.
But it was the winger's third that was his best, with he and Kennedy combining to go 80 metres after a Newcastle fumble.
8°C