The mystery of what's keeping nose tackle Louis Nix out so long has been sort of solved.
Texans coach Bill O'Brien said during his daily news conference that Nix is recovering from arthroscopic knee surgery he had during the offseason. Nix dealt with a knee issue that kept him out of most of the Texans' spring practices.
The Texans drafted Nix in the third round this May and he is currently on the physically unable to perform list as he recovers from that surgery.
This isn't the first time Nix has had knee issues. He suffered a torn meniscus last season while he was at Notre Dame, and had season-ending surgery to repair that injury.
O'Brien said the Texans planned the surgery early so Nix's recovery could wrap up before the season began. Nix is the second 2014 draft pick known to have had offseason surgery since being drafted. First overall pick Jadeveon Clowney had sports hernia surgery in June.