The Bears fear Harris tore his triceps during Monday's loss to the Vikings, Kevin Fishbain of The Athletic reports.
The Bears expect this to be the diagnosis, and they're running further tests to confirm it. Harris has functioned as a punt-return specialist for three games, and he was impressive at the position with 8.1 yards per return. If he's ruled out for the season, expect Darnell Mooney and Anthony Miller to step into the returner role.