It's simply a reality of having a running back who is approaching age 30 -- Foster will turn 29 later this month.
What Foster is dealing with now is not the kind of soft tissue injury they'd all accepted he'd have to work through every once in a while. A groin injury that requires surgery, as Foster's likely will, involves a significant tear. It'd be a mischaracterization to liken this injury to the hamstring and groin injuries that caused Foster to miss parts of three games and all of three more last season.
That being said, the Texans now have to figure out how to replace Foster for part of the season.
It takes more than one player because, when healthy, Foster can do everything and do it well. Last year they used two backups to fill the void -- Alfred Blue on first and second downs and Jonathan Grimes on passing downs. Blue has worked on developing the skills he needs to be a three-down back, and this could offer a good test to see the progress he's made this year. Blue was carted off the practice field yesterday, but just had a cramp. It's hot out there, even at night.
Chris Polk will be interesting to watch. The Texans signed him in free agency this year. He had a hamstring issue that's limited him in practice lately, but that's not a long-term concern.
Bringing in another player to offer depth is an option I think the Texans will consider. Our Adam Caplan offered this list of available running backs.
Best available RBs for #Texans: S. Jackson, A. Bradshaw (1-gm susp.), C. Johnson, Pierre Thomas, S. Greene, B. Tate, K. Moreno, R. Rice.— Adam Caplan (@caplannfl) August 4, 2015
The two who would surprise me the most are Ray Rice and Ben Tate. Rice because Texans owner Bob McNair has told me repeatedly that he has zero tolerance for domestic violence. Tate would surprise me because he was a free agent the year that this staff came in and they weren't interested in re-signing him.
I've created a chart on the rest. They all have some issues or they wouldn't be available right now, but could offer the kind of experience the Texans don't really have on the roster right now.