Bears film study: David Montgomery in I-formation needs to stay

There’s no doubt Bears coach Matt Nagy loves to throw and would do so as often as possible, so it was an admirable show of his dedication to the run that the offense opened in the I-formation against the Chargers.

And then it worked.

The formation that seems so far outside of Nagy’s wheelhouse might be exactly what the Bears need. A review of the film from their 17-16 loss Sunday showed David Montgomery gained 43 yards on six carries out of the I.

The Bears also ran Mike Davis in that formation twice for three yards, and the one time they used it as a decoy to pass, Mitch Trubisky hit Allen Robinson for 31 yards. That pushed them to 77 yards on nine I-formation plays.

‘‘Back in the day, that used to be three yards and a cloud of dust,’’ Nagy said Monday. ‘‘So it sounds like eight yards and a cloud of dust now. I like that.’’

He balked at the notion that it’s an unnatural play-call for him. If that’s a path to success for his struggling offense, he can’t afford to let personal preference get in the way.

‘‘Whatever works, I’m down with,’’ Nagy said. ‘‘I don’t know if we’ll do more of it or less of it. We’ll have to just wait and see.’’

It seems likely he’ll use the I-formation for 10 or so plays Sunday against the Eagles. When the offense ranks 28th in total yardage and 27th in points, anything that proves effective can become an instant staple.

Trubisky’s troubles

Another thing pushing coach Matt Nagy out of his comfort zone is Mitch Trubisky. The Bears have been ultra-cautious in what they ask Trubisky to do, but even that has been dicey.

Trubisky ranks 36th of 40 in air yards per completion among quarterbacks who have thrown at least 60 passes. His average completion has traveled 4.3 yards beyond the line of scrimmage, and that went up from 3.9 heading into the game against the Chargers.

Trubisky completed 8 of 8 passes behind the line of scrimmage and went 3-for-5 on throws of five yards or fewer past the line. He was a respectable 7-for-10 on passes 10 yards or deeper but made two devastating mistakes in that range.

Early in the fourth quarter, with the Bears having a chance to take a two-score lead, Trubisky badly misread the coverage and threw an interception.

He had Trey Burton, Allen Robinson and Anthony Miller on the right side, and, as the play unfolded, it appeared to him Miller was taking Chargers cornerback Casey Hayward with him deep up the middle.

That would have left Burton open for a 23-yard catch on the sideline, but Hayward stuck to Burton and trusted safety Rayshawn Jenkins to pick up Miller, which he did. Trubisky didn’t anticipate it and served up an easy pick to Hayward.

‘‘So when [the defender] falls off on that . . . that’s one where [you] dump it down,’’ Nagy said. “It’s 16-10, you dump it down, and we live to see another down.’’

Trubisky’s other deep-ball miscue squandered a perfectly schemed and executed play midway through the fourth. He missed on a throw every NFL quarterback should make.

Everything clicked to get Taylor Gabriel matched up against Chargers linebacker Thomas Davis Sr., and Gabriel blew him away. It would have been a 58-yard touchdown — probably the ‘‘dagger’’ in the game, Nagy said — had Trubisky not sailed it over him.

‘‘He truly missed that one,’’ Nagy said. ‘‘He knew it right away. We all knew it.’’

Defensive ups and downs

It wasn’t a flawless performance by the defense, but it looked much more like its usual standard than it had in the previous two games. The defense held Philip Rivers to 201 passing yards and an 82.7 passer rating, shut down Melvin Gordon with the exception of one long touchdown run and kept the Bears alive with a late stop.

The Bears were down 17-16, and the Chargers had the ball at their own 15 with 2:04 left. A single first down would’ve left the Bears with no more than 30 to 37 seconds, but the defense got a three-and-out and gave Mitch Trubisky a chance with 1:33 left.

Khalil Mack came up with the team’s first sack of the day by plowing through left tackle Russell Okung. Two amazing things about Mack are his speed and vise-like grip. Once he got a hand on Rivers’ shoulder, it was over.

From there, Kyle Fuller played back on Keenan Allen and came up for a quick stop on a four-yard catch. Rivers nearly got the first down on a pass to Hunter Henry, who needed to reach the 25, but Fuller hit him at the 21, Buster Skrine hit him at the 22 and Eddie Jackson and Prince Amukamara brought him down at the 24.