Coach Matt Nagy made the announcement Wednesday before practice, adding that veteran Nick Foles will serve as the Bears' No. 2 quarterback in Cleveland.
Dalton performed well in last Sunday's home-opening win over the Bengals, completing 9 of 11 passes for 56 yards with one touchdown and a 118.2 passer rating. But the 11-year veteran injured his knee at the end of a 14-yard scramble early in the second quarter. He returned for one series but then exited and sat out the rest of the game.
"Andy is still battling through his injury," Nagy said. "We're not expecting him to practice today or to have him available this week. He'll be week-to-week. Justin is going to be our starter and his prep basically starts right now … It's a great opportunity for Justin and for all of us as a staff to be able to take this thing and see where he goes with this."
Nagy stressed that "when Andy is healthy, our plan continues for him to be the starter." But the focus this week will be spent solely on preparing Fields for his first NFL start.
"He's [been] able to do this in training camp, he's [been] able to get out and play in the preseason and he made some good plays," Nagy said. "But now he gets to do it for real, quote-unquote."
Nagy acknowledged the excitement level that's building in anticipation of Fields' first pro start. The Bears traded up nine spots in the first round to No. 11 to land the talented dual-quarterback, who was one of college football's most explosive stars at Ohio State.
"It's unfortunate what happened to Andy because Andy was really playing well there at the beginning part of that game," Nagy said. "Andy is a very tough player and a team guy and I know he's been very supportive here moving forward with Justin. But there is excitement. Justin prepares well. This is going to be his first time to truly prepare as the starter and see what it's like every single day to do that stuff mentally and physically in practice.
"The other thing is this is obviously big news to a lot of people and to him. I think the biggest thing we can help him with [concerning] the distraction part is making sure you take care of what you need to take care of, keep him insulated, and that's what we'll do, and then go out and learn and have fun. When you're playing, go have fun, be a great teammate, and that's probably one of Justin's greatest strengths."
Fields and the Bears should benefit from knowing midweek that he'll be Sunday's starter—versus the situation last weekend when he entered the game following Dalton's injury. It will allow Nagy and his staff to develop a game plan that takes advantage of what the young quarterback does well.
"We were able to really get a feel for the things that we like or don't like with him in training camp and the preseason," Nagy said. "So now we get together as a staff and we just talk through the things that we think he does well for us, and you've got to put everything into play … and be able to give him and our offense the best opportunity possible."
Nagy knows that it's important not to put too much on Fields' plate.
"We understand the significance of not giving him too much so he plays slow," Nagy said. "We all want Justin to play really well. We know on the front end there's going to be mistakes. That's going to happen. We understand that. But we've got to try to reduce and eliminate those as we go throughout the year when he's going … And then every time he's there playing, play hard, do your thing and just be the best quarterback you can be."
Asked what advice he'd give Fields heading into Sunday's game, Nagy said: "Just trust your instincts. Play the way you've played your entire career. And play loose. Have fun, too. Go out there and trust your teammates. Don't try to be a hero. Just go out there and play. Be a great quarterback for this game and see where it takes you the rest of the year."
The Bears hit the practice fields at Halas Hall Wednesday afternoon as they continue to get ready for Sunday's matchup with the Browns in Cleveland.