Speculation has been mounting in recent weeks over whether Tedesco or Ryan Papenhuyzen will line up at the back, with the Storm star putting on multiple strong performances.
Papenhuyzen was voted best on ground in last week's 60-point demolition of the New Zealand Warriors, and was at his best again on Sunday afternoon in a strong win against the Newcastle Knigths, with the Storm running up another half-century worth of points.
When asked on Channel 9s Wide World of Sports however, Fitler said Tedesco was the captain and would be there.
"James Tedesco is our captain," Fittler said bluntly.
"If he is fit and healthy, he will be our fullback."
Fittler didn't rule out picking Papenhuyzen though, suggesting he is one of the most dangerous players in the competition and could be in line for the number 14 jumper.
"He's always there Paps [Ryan Papenhuyzen]," Fittler said.
"The biggest thing he has on his side is that he played so long in that number 14 role.
"We have a side who won last year, so you like to give them as much chance as possible, but he has the ability to play a few positions and you can see what he does. He has the ability to turn opportunities all over the field, not just off the dummy half, but off wingers, off centres, he creates tries.
"If you're getting good ball, Ryan Papenhuyzen is the most dangerous person in the competition.
It has been heavily suggested that Papenhuyzen could be in a race with Nicho Hynes for the number 14 jersey, with the former Melbourne teammate shifting to the Cronulla Sharks this season where he is now playing in the halves, guiding the Sharks to the top four early in the season.