Texans receiver Andre Johnson downplayed the severity of the injury.
"If it was serious, we'd know it," he told reporters. "This wasn't serious."
Kubiak said the running back, who rushed for 1,424 yards and 15 touchdowns last season, is considered day to day for the rest of the Texans' OTA practices, which run through Thursday.
"It's always concerning," Kubiak told reporters of Foster's injury. "We'll see what's wrong, see what happens."