Bears to start rookie quarterback Mitch Trubisky Week 5

The Bears rookie will make his NFL starting debut on “Monday Night Football” on Oct. 9 against the Vikings.

A change, though, was expected after Mike Glennon’s four-turnover performance in a blowout loss to the rival Packers on Thursday night. There was growing discontent with his play since Week 2.

The Bears had hoped that Glennon, who was guaranteed $18.5 million in March, could start all season, allowing Trubisky to sit and learn. But Glennon has struggled mightily.

Glennon has completed 93 of 140 passes for 833 yards, four touchdowns and five interceptions. He also has lost three fumbles. Overall, he has failed to improve markedly since the start of training camp. After four starts, the Bears can no longer attribute his mistakes to rust.

Meanwhile, Trubisky, the No. 2 overall pick in the draft, has progressed faster than the team expected.