Sanchez has appeared in one game and is hitless in two at-bats. The move is retroactive to Wednesday.
Greene was released by Houston in spring training and signed to a minor league contract by the White Sox on April 4. He was batting .265 in eight games with Charlotte. Greene, taken by St. Louis in the first round of the 2005 draft, is a career .224 hitter in four seasons.
Left-hander Charlie Leesman was designated for assignment Sunday to make room for Greene on the 40-man roster. Leesman pitched at Charlotte last season and is currently coming back from knee surgery.