The tight end is out for at least eight weeks after being placed on the injured reserve designated to return list with a fibula fracture.
The 27-year-old told the team's website: "I would say probably 15 to 20 more plays, maybe. We've obviously run a lot of two and three tight end sets, so I've been able to be in there a lot. But obviously, with Owen out, it's a shame, but I'll probably be in there another 20 plays or so."
Head coach Gary Kubiak added: "[Graham is] like a starter and so he becomes our starter. Obviously, we'll miss OD. He's a big part of what we do offensively and we've had some challenges offensively."
The Texans play the St Louis Rams tomorrow.