The coach said that Trubisky will start the game.
Trubisky, who was voted one of the five captains on Monday, was listed as the starter on the depth chart.
"Mitch has shown us what he can do and we're just really comfortable with what he has shown us," said the coach.
The Pittsburgh Steelers are pleased with the development of Kenny Pickett, who will be their backup quarterback.
The third quarterback is a veteran.
Rudolph was listed as the backup on Monday's initial depth chart. The coach said the mix-up was a "clerical error" and that the order was adjusted before the news conference.
A veteran signed to a two-year, $14.2 million contract in free agency, Trubisky was the favorite to win the race. After a year as Josh Allen's backup with the Buffalo Bills, Mitchell Trubisky was traded to Pittsburgh.
He started all three preseason games and played in all of them. In the final preseason game, he played the entire first half and closed the second quarter with a 1-minute, 20-second touchdown drive.
Brooke Pryor was a contributor.