Buffalo Bills running back Fred Jackson could miss two weeks after suffering a hamstring injury at practice on Friday.

Jackson suffered the injury midway through the practice session and didn't return. The 34-year-old is Buffalo's No. 2 running back behind starter LeSean McCoy.

Bills coach Rex Ryan says Jackson's injury is "not a terrible one," but he will probably miss two weeks.

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Jackson has been one of Buffalo's top contributors on offense over the past eight seasons. The injury further depletes Buffalo's depth at running back; backup Anthony Dixon is expected to miss up to a month with a calf injury.

With numbers low at running back, the Bills signed undrafted free agent Bronson Hill on Thursday.