Trindall suffered a dislocated shoulder as the Sharks' second straight slip-up allowed the Dolphins to hold on to the all-important fourth spot with three rounds remaining before the finals.
Cronulla will rue not finding a match-winner, despite being camped on Canberra's line, set after set, for the final 10 minutes.
But the Sharks' mounting injury toll, and especially Trindall's, is of more concern for coach Craig Fitzgibbon, who has now watched his faltering side fumble and bumble their way to consecutive losses to sides well out of finals contention.
Trindall lasted less than 10 minutes before trudging off.
Initial reports were promising, with the shoulder quickly put back in, but Fitzgibbon was unsure how long his key playmaker will be sidelined.
"Obviously, it's pretty important to us," Fitzgibbon said.
"Went out, went in straight away immediately, so usually when they get stuck out for like a long period of time, it's worse.
"So no one has any idea at this stage, but it definitely went out and straight back in, so that's a good sign for us there."
Fitzgibbon still has his fingers crossed that Trindall might even be available to face the Gold Coast next week, but the more likely scenario is the classy five-eighth will be sidelined for at least two or three games.
The Sharks will certainly need Trindall back on deck ASAP after halfback Nicho Hynes was unable to orchestrate an against-the-odds victory on his own.
Already without suspended forward enforcer Addin Fonua-Blake and injured centre Jesse Ramien, the Sharks looked vulnerable from the minute Trindall went off.
The afternoon had started brightly enough for Cronulla, with a Hynes penalty preceding a lovely chip-and-regather try for Trindall in the fifth minute.
But from 8-0 up, the Sharks lost their way. Tries to Xavier Savage, Owen Pattie and Jed Stuart helped the Raiders to an 18-8 lead.
The Sharks briefly regained the lead with replies either side of halftime to Teig Wilton and William Kennedy.
But a soft try to Joseph Tapine under the sticks put the Raiders back in front.
There was a huge moment with seven minutes remaining when video replays looked to have shown Ronaldo Mulitalo contorting his body and planting the ball down for a match-levelling try.
But The Bunker went with referee Gerard Sutton's on-field "no try" call.
The Sharks were privately livid with Sutton's performance, but Fitzgibbon refused to blame the referee for his side's costly defeat.
"I'm not a sook with calls because I just reckon you'll win some, you lose some over the course of the year," he said.
"Canberra were the better team. They don't deserve to win via a shit call, (but) like that was just the way it was.
"But also there were some calls there, oh man, like the flops that we don't get, and then we cop the same thing in return at the end of a set where they sting you.
"But I'm not blaming the referee."
The near-miss and consecutive defeats to last-placed St George Illawarra and now Canberra leaves the Sharks likely needing to beat the Titans, Parramatta and Melbourne to earn a double-chance in the playoffs.
No team has ever won the NRL premiership from outside the top four.
