It’s finally Mitch Trubisky time.

The Bears rookie will make his NFL starting debut on “Monday Night Football” on Oct. 9 against the Vikings, two league sources told the Sun-Times. Players were still being informed of the quarterback change as of Monday morning. The team was off over the weekend.

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. ESPN was the first to report the news of the Bears’ quarterback change.

Coach John Fox tip-toed around the subject of a quarterback change last Friday, but he definitely opened the door for it. His once-staunch support for Glennon had dissipated.

“We’re looking at everything,” Fox said then.

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, Glennon 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. Trubisky was named the Bears’ backup after playing well in the preseason. His responsibilities also expanded to include running the scout team.

Fox described Trubisky as a player who can “raise all boats.” While Glennon was struggling in real games, Trubisky was impressing everyone — coaches, players, the front office, etc. — in practice.

“[It’s] kind of how he conducted himself, how he went about it,” Fox said Sept. 8. “I think very early on for us as coaches I think we saw the tenacity with which he goes about it and the maturity with which he prepares.

“And then there’s just a kind of an ‘it’ factor in how you relate to people around you and how people feed off you. That was pretty evident early, too.”