Nix was born in Dallas, Texas, and still makes his offseason home there. He attended Midland High School in Midland, Texas, the hometown of First Lady Laura Bush, a point that President George W. Bush made to his wife while meeting with the Olympic team on August 11, 2008, in Beijing. Nix began the 2008 season as the Colorado Rockies starting second baseman but over the next month, he saw his playing time diminish. On April 26, 2008, Nix was designated for assignment. He had played in 17 games and batted .111 with no home runs. On April 30 he cleared waivers and was sent outright to Triple-A.