Breaking down film from the Bears’ 17-7 loss Sunday to the Rams to see exactly how quarterback Mitch Trubisky suffered a hip pointer, how coach Matt Nagy used him after the injury and signs that the injury was deteriorating during the game.

How Trubisky got hurt

Trubisky suffered the hip injury because the Bears couldn’t get open against zone defense.

Facing a four-man rush on third-and-eight with 39 seconds left in the first half, the Bears lined up three receivers to the left and tight end Ben Braunecker in the right slot.

Three seconds after the snap, all four were covered when Trubisky scrambled to his right. The only potential pass-catchers at that point were Braunecker and running back David Montgomery, who had slipped out into the right flat.

Trubisky ran right but stopped at the Rams’ 40-yard line, a yard before the line of scrimmage, and ran parallel with the yard-line marker. He looked downfield, but no one was open. He didn’t want to step out of bounds before fourth down and apparently didn’t want to throw the ball away, either.

He stepped back to the 42 to avoid diving outside linebacker Dante Fowler a foot from the Bears’ sideline. He ducked under cornerback Troy Hill but was sacked by defensive end Michael Brockers. With his back turned, Trubisky was hit in his lower back and right hip by Brockers’ left knee.

The Bears brought their offense onto the field for fourth-and-10 before sprinting them off in favor of the punt team. Trubisky ran gingerly to the sideline. On film, trainer Andre Tucker can be seen walking up to Trubisky, who moments later is shown looking uncomfortable on the sideline.

Signs of discomfort

Nagy was told about the injury at halftime but said he didn’t start paying particular attention to it until Trubisky said his hip stiffened up further in the third and fourth quarters. But Trubisky looked uncomfortable even when just handing the ball off early in the second half.

About 5½ minutes into the third quarter, Trubisky, in a shotgun formation, handed off to running back Tarik Cohen for a 12-yard draw.

‘‘He’s supposed to stand up and then bend down and then hand the ball off,’’ Nagy said. ‘‘He couldn’t even do that.’’

Trubisky looked as though he was winging passes as the game went on.

‘‘I think I noticed a little bit throwing to the left — like, with his hip — when he was trying to open his hip to throw,’’ Nagy said after the game.

After the Bears’ touchdown on the first drive of the third quarter, Trubisky threw seven passes to his left. He completed three for only 11 yards.

‘‘The movement of the hips, everything was a lot of arm,’’ Nagy said. ‘‘There wasn’t much stepping into throws.’’

By the end of the game, Nagy said, the hip made it difficult for Trubisky to sit on the bench. The airplane ride home was uncomfortable, too.

Option? Really?

Nagy’s decision to run speed option to the short side of the field on third-and-one made little sense in the moment. It seemed even worse once the team revealed Trubisky was hurting.

With about 3½ minutes left in the third quarter — that’s six minutes after he looked pained handing the ball off on the draw to Cohen — Trubisky lined up with Montgomery behind him. In a pistol formation (a shorter shotgun), the Bears ran speed option left from the left hash. And Trubisky ran it terribly.

A quarterback is taught to run toward the edge rusher to force him to make a decision to cover either him or the running back. Instead, Trubisky took four steps directly to his left — not toward the line of scrimmage — and pitched to Montgomery, who was swallowed up for a three-yard loss.

Rams outside linebacker Samson Ebukam, who wasn’t forced to make a decision by Trubisky, was able to cover both players.

‘‘I should’ve attacked [Ebukam] a little more and pitched the ball,’’ Trubisky said after the game. ‘‘I pitched it too early, which is why they made the play.’’

Trubisky was hurt, of course, though the world outside the Bears’ bench didn’t know it.

Nagy called the play anyway, saying Monday that Trubisky’s health was somewhere ‘‘in the middle’’ — between the uncomfortable feeling he had at halftime and the more severe tightness he had in the fourth quarter.

‘‘You can always look back and second-guess the type of play-calls,’’ Nagy said. ‘‘Even without an injury, I still sometimes to myself wish in that position you’d made a different play-call.’’