Houston Texans coach Gary Kubiak has admitted that he is unsure about a return date for running back Arian Foster.

Foster was initially expected to return to training on Monday but Kubiak said that he will have to slowly reintroduce the player if he is not to suffer further setbacks.

"He's had some injections to try to alleviate some of the soreness," ESPN quotes Kubiak as saying. "The way I understand it we're trying to [work through] the injection process.

"I'm not [able to set a return] yet because I see him work. I see what he's going through. I am concerned about repetitions.

"That's just me as a coach. We gotta do what we gotta do. We're trying to do the smart thing here."

Foster played 16 games for the Texans last season and carried for 1,424 yards.