Bill O'Brien cheekily said on Tuesday the injury wasn't "life-threatening." However, for a running back who has gone through myriad injuries over the last several years, including hamstring issues, it's fair to be concerned about every tweak and injury.
The Texans' lead runner dealt with injures last summer and ended up missing eight games in 2013 due to a back injury.
Houston's offense needs a healthy Foster to have a chance in 2014. Ryan Fitzpatrick hasn't shown an ability to carry an offense, and there are depth questions in the backfield.
Receiver Andre Johnson, who has also been dealing with a hamstring injury, missed his third straight day of work.