The 2014 rookie class was a bright spot in Saturday's win over Atlanta.
Third-round nose tackle
"He's got a lot to do to catch up," O'Brien said, while acknowledging the rookie was closer to coming back.
When asked about what main things Nix needed to work on improving, O'Brien ticked off a list of a few things.
"Football shape," O'Brien said. "Football knowledge. NFL knowledge. What it takes to play in this League, day in and day out."
Nix passed a physical and was added to the active roster on Tuesday morning. He was limited in practice during the week versus Atlanta.
The Texans will meet as a team on Monday morning and then fly to Denver. They'll practice against the Broncos on Tuesday, Wednesday and Thursday.