According to Jonathan Jones of CBS Sports, Nagy said: "We believe it's going to play itself out. It's going to be completely open."
Trubisky was the No. 2 overall pick in the 2017 NFL draft by the Bears and has been the team's starter for most of the past three seasons, but Chicago acquired Foles from the Jacksonville Jaguars in March for a 2020 fourth-round pick.
After showing promise in 2018 by throwing 24 touchdowns passes, going 11-3 as a starter and leading the Bears to an NFC North title and playoff berth, Trubisky struggled mightily for much of last season.
He went just 8-7 as a starter and completed 63.2 percent of his passes for 3,138 yards, 17 touchdowns and 10 picks.
Chicago ranked just 25th in passing yardage and 29th in scoring last season, which prompted the front office to give the offensive-minded Nagy another option under center.
The soon-to-be-26-year-old Trubisky may still have some untapped potential, but in Foles, the Bears have a 31-year-old veteran who led the Philadelphia Eagles to a Super Bowl win three seasons ago and was named Super Bowl MVP.
Foles led the Eagles on a magical run in 2017 and finished those playoffs with 971 passing yards, six touchdowns and one interception, but that is something of a distant memory considering what Foles did last season in Jacksonville.
The Jags signed Foles to a four-year, $88 million contract in hopes that he would be the savior at quarterback, but he was injured for much of the year and ineffective when he played.
Foles went 0-4 in four starts and completed 65.8 percent of his passes for 736 yards, three touchdowns and two interceptions. Foles ultimately lost the starting job to rookie sixth-round pick Gardner Minshew, and the Jaguars quickly moved on by trading Foles to Chicago.
Nagy was the Kansas City Chiefs quarterbacks coach from 2013-15 and their offensive coordinator from 2016-17, so his philosophy lines up with Chiefs head coach Andy Reid and Eagles head coach Doug Pederson, the latter of whom was Foles' coach when he won the Super Bowl in Philly.
Foles should be comfortable in Nagy's offense, and that could give him a leg up in the competition against Trubisky, but Trubisky is entering the final year of his contract, and the Bears may want to see what they have on him before officially deciding to move on.
The lack of preseason games will make for a unique competition, as both quarterbacks will be tasked with impressing in practice situations rather than actual games.