(AP Photo/Charlie Riedel)

KANSAS CITY, Mo. (AP) Kyle Shanahan was watching as Jimmy Garoppolo scrambled toward the 49ers sideline and, rather than safely duck out of bounds, stepped back to his right and took a wicked shot from Steven Nelson.

At first, the San Francisco coach thought his quarterback had sustained a concussion.

Turns out it may have been a season-ending knee injury.

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