With calls already growing for Fittler to dump the NSW captain from State of Origin III, Tedesco's first-half shocker at Allianz Stadium allowed the Raiders to race out to an ultimately match-winning 18-0 lead inside half an hour on Sunday night.
Setting the tone for his poor performance, a dreadful mix-up between Tedesco and winger Junior Pauga gifted Canberra the first points of the game in the fifth minute.
The pair made a meal of a Canberra bomb, leaving Egan Butcher with no choice but to retrieve the ball from an offside position and hand Jarrod Croker two points for the penalty.
Much worse was to follow for Tedesco with Jack Wighton outleaping the jump-shy fullback to score off another Fogarty high kick moments later.
By the time Tedesco was beaten in the air a third time, enabling Matthew Timoko to score Canebrra's third try following a long-range effort to Albert Hopoate, Trent Robinson's team looked like shot Roosters.
Joey Manu did his best to save Tedesco and the Tricolours' blushes with two superb tries in four minutes either side of halftime.
The 2022 world player of the year was denied a third midway through the second half as Canberra withstood the fightback to leave the Roosters - many pundits' pre-season title favourites - languishing in 12th spot, with more defeats than wins entering round 18.
In a huge concern for Robinson, the Roosters continue to possess the worst attacking record in the competition ahead of looming battles with heavyweights Melbourne, Brisbane and Parramatta.
With a poor points differential, the Roosters will probably need to win six of their remaining nine matches to scrape into the top eight and make the finals.
Compounding their woes, star back-rower Angus Crichton was forced out of Sunday's game at halftime with a knee injury and Victor Radley was placed on report for a high tackle on Croker.
But Robinson isn't the only coach with an almighty problem to solve.
Fittler faces a huge Origin selection dilemma.
With the series already lost and his six-year tenure as Blues boss seemingly coming to an end, Fittler is now also under increasing pressure to end Tedesco's decorated NSW career.
A concerted push for Dylan Edwards to be given a chance in place of the Blues' 21-game stalwart and skipper gained more momentum with the Penrith dynamo again starring in the understrength Panthers' 20-12 win over Newcastle on Saturday night.
Canberra's stocks, meanwhile, continue to rise.
Despite losing powerhouse prop Josh Papali'i to a hamstring injury inside the first 10 minutes, the Raiders' handy away win vaults Ricky Stuart's side from ninth to sixth on the ladder.
