The running back, who has also been dealing with thumb and chest injuries, is expected to start this weekend despite the knocks.
Head coach Gary Kubiak told reporters: "He has a sore hamstring from [Wednesday] and he could have practised, but we just held him out.
"He's really been a two-day-a-week practice guy anyways. I don't have any big concerns. I expect him back out there tomorrow."
Foster has 117 rushing yards, 183 receiving yards and two touchdowns so far this season.