Foster said he will undergo an MRI exam Monday.
Foster was on crutches in the locker room after the game. He sat at his locker for a while, put a towel over his head and dropped his head into his hands for a few seconds.
When asked if he knows how serious the injury is, he said, "Not yet, but it's not good."
"I feel terrible for him," Texans head coach Bill O'Brien said. "He's done a lot for us in the two years I've been here. I hate that part of the game."
The injury happened with less than five minutes remaining in the game and the Texans trailing 44-20. Foster motioned out wide and went down as he began his route. He was not contacted on the play.
"Just a routine play," Foster said. "Trying to make a cut, gave out on me."
The Texans scored on the next play while Foster was taken from the sideline on a cart. O'Brien was asked if he regretted having Foster on the field with the game out of reach and with so little time left.
"No, I thought at that point it was ... I think there were between four and five minutes left in the game, and we were trying to get a touchdown there," O'Brien said. "So, no."
Foster finished with 125 all-purpose yards and two touchdowns.
He missed the first three games of the season with a groin injury he suffered during training camp. Foster had surgery to reattach a muscle to the bone on Aug. 7. He returned on Oct. 4 against the Atlanta Falcons, a game the Texans lost 48-21. Since 2011, Foster has missed at least one game due to injury in all but one season.
This season, Foster has 163 yards rushing on 63 carries.
The Associated Press contributed to this report.