The center has missed the last two months with thigh and knee problems, while Smith has also been struggling with a lingering knee injury.
The coach told the Houston Chronicle: "Everything is not a definite. We're 'hoping for' is what I'm getting. We really need Greg Smith or Omer to get back. They're starting to do a little bit more. Both have been without a basketball in their hand, actual live playing for so long."
The Rockets host the Phoenix Suns later today.