Nix was a third-round pick by Houston in May's NFL draft. He played collegiately at Notre Dame.
The rookie had arthroscopic knee surgery before training camp and wasn't able to participate in camp until Aug. 12. He was inactive for Houston's first three games this season.
Pickett has played 13 years in the NFL, including spending the last eight with the Packers. The 34-year-old started all 16 regular-season games for Green Bay in each of the last two seasons.
The Texans are 2-1 and host the Buffalo Bills on Sunday.
- Molly Geary