The Chicago Bears’ 24-14 victory over the Detroit Lions offered a glimmer of hope that the combination of quarterback Justin Fields and offensive coordinator Bill Lazor may actually provide Chicago with an offense that’s capable of scoring points—maybe even against talented defenses. But any positive momentum gained from Week 4’s win was lost when running back David Montgomery went down with a knee injury.

NFL insiders Ian Rapoport and Adam Schefter have both said the Bears believe Montgomery dodged a serious injury, but he did suffer a knee injury that should keep him sidelined for at least a couple of weeks. Matt Nagy met with the media Monday morning and said the Bears are holding out hope that Montgomery will be back soon.

Montgomery was the engine that made the Bears’ offense go on Sunday prior to exiting the game. His 23 carries for 106 yards and two touchdowns set the table for Fields to have a much-improved second start and provided Chicago with an offensive identity capable of scaring opposing defenders.

Losing Montgomery from the lineup, even if just for a week or two, is devastating. He’s logged 166 snaps through four games, 95 more than the next closest running back, Damien Williams. He not only has been a supremely productive runner (he’s fifth in the NFL in rushing yards with 309); he’s also the Bears’ highest-graded pass-blocker, per Pro Football Focus, with an 85.9 grade.

There’s also the on-field juice Montgomery brings to the field. His teammates feed off of his energy and physical style of play.

Assuming Montgomery will be sidelined for a few weeks, the next man up on the depth chart is Williams, who exited Sunday’s win with an injury of his own (thigh bruise). Williams is a battle-tested veteran who elevated his game during the 2019 season with the Kansas City Chiefs. He’s been effective this year in relief of Montgomery, averaging 4.6 yards per carry. He had an impressive touchdown run against Detroit, too:

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Williams was signed during the offseason for this exact moment. He’s familiar with Nagy’s system and even with Lazor calling plays, so there won’t be much of a change needed, strategically when he’s in the lineup. But it’d be dishonest to say he’s talented enough for the offense not to feel Montgomery’s absence.

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Behind Williams is rookie Khalil Herbert, who’s flashed as Chicago’s primary kick returner this season. He had some good moments as a runner in the preseason too, but he’s an untested first-year player who (probably) can’t be trusted as a primary piece of the offense just yet. Nagy said Monday that the Bears are confident in Herbert’s ability, going as far as to compare a potential Herbert opportunity to Kareem Hunt’s emergence when he filled in for Chiefs starter Spencer Ware in 2017. It’s high praise for Herbert and suggests the coaches believe in him.

I’m a big fan of Herbert’s skill set and think he has a very high ceiling—there’s a good chance he’ll be the Bears’ RB2 next season. But just one month into his rookie year and with only 10 offensive snaps on his resume, I’d expect a heavy dose of Williams while Montgomery is out.

There’s no way around it. The Bears are going to struggle without Montgomery toting the rock for a few weeks. And this is another reason why it’s so important that Fields remain the starting quarterback. He can make up for some of Montgomery’s lost rushing production with designed quarterback runs, something that just isn’t part of the playbook with Dalton behind center.

We’ll soon find out how many weeks Montgomery will miss. Whether it’s one week, one month, or longer, the fear and anxiety that’s emerged because of his expected absence is further proof that he might just be the Bears’ most important player right now.