Blake Tekotte came to the White Sox last offseason from the San Diego Padres in exchange for Brandon Kloess. In 20 games with the Sox last season, Tekotte hit .226/.306/ .355 with one home run and one stolen base in four attempts. While he had been on the 25-man roster at multiple points during the season, he wasn't included in the September callups, putting his future with the team in question.
Switch-hitting first baseman Mike McDade has been the man of mystery on the White Sox 40-man roster for much of the past season. He began the 2013 season in the Indians organization after several seasons with the Blue Jays. After hitting .230/.313/.284 in April for Triple-A Columbus, the Indians released him. The Sox swooped in and signed McDade in early May and added him to the 40-man roster. He then hit .254/.313/.390 for Charlotte. Combine that with the signing of Jose Abreu and he became a likely candidate to be removed from the 40-man roster. That day has finally come.
With this move, the 40-man roster goes back to 38. The White Sox press release from the Sox says 37, but the Ronald Belisario deal hasn't been finalized, so pencil him in. These moves mean the Sox are eligible for the Rule 5 draft again.
P.S. Thanks Jim, I wrote Donald Belisario twice.