Humber pitched the 21st perfect game in major league history on April 21 at Seattle, but outside of making history, his season was a disappointment. The right-hander posted a 6.44 ERA and missed a month with an elbow flexor strain, ultimately losing his spot in the rotation.
The 29-year-old Texas native, who pitched for Rice University in Houston, will now be a member of the hometown Astros.
Johnson, 33, remained stuck at Triple-A Charlotte this past season, hitting 28 home runs with 85 RBIs. He was eventually a September call-up, hitting three home runs against the Cleveland Indians on the final day of the season.
Carter, 26, was a 26th-round pick by the White Sox in the 2005 draft and pitched the entire 2012 season at Charlotte where he posted a 4-6 record with a 4.60 ERA. All but one of his 39 appearances were in relief. Carter had a 4.70 ERA over seven minor league seasons in the White Sox system.
The activity opened three spots on the White Sox’s 40-man roster, giving them room to operate at next week’s annual winter meetings in Nashville.