After spending the preseason as the team's designated No. 3 quarterback, coach John Fox announced Wednesday the rookie finally overtook Mark Sanchez for the backup gig.
"He earned that spot," Fox said of Trubisky.
Added the coach: "Everyone was impressed how fast he picked things up."
The No. 2 overall pick shined in early preseason outings, displaying pinpoint accuracy, mobility and confidence running the offense. Trubisky completed 67 percent of his preseason passes for 364 yards and three touchdowns with zero interceptions.
Moving Trubisky to the backup role before the season opener puts him a step from taking over for starter Mike Glennon. Fox added Sanchez would lead the scout team.
When asked on Wednesday if the Bears would have a package of plays for the rookie quarterback, Fox responded: "If there were, I surely wouldn't mention that in this setting," via Zach Zaidman of the Bears radio network.
Elevating Trubisky to backup duties is the next step in the rookie's inevitable rise to the starting job. When he makes his first start depends on how Glennon fairs to start the season.
Chicago opens the season Sunday at home against the reigning NFC champion Atlanta Falcons.