The Kansas City Chiefs have listed Jamaal Charles as "day to day" after he limped out of training camp with a foot injury yesterday.
The running back was missing from today's practice, despite x-rays ruling out a fracture or Lisfranc injury.
The team's trainer, Rick Burkholder, told The Kansas City Star: "His ankle ligaments were fine. He had some pain on the outside bone of his foot. We did an X-ray. That was negative.
"There's a tendon that attaches right at that spot and that's what is sore right now. That's why we call it a strain."
The injury could keep Charles, who recorded 1,509 rushing yards for the Chiefs last season, out of the side's pre-season game against the San Francisco 49ers later this week.