With Brian Schneider ready to come off the disabled list, the Mets were looking at having three catchers on their roster or sending rookie Omir Santos back to the minors despite his solid play.
Santos homered in the fifth inning and drove in the winning run with a single in the 11th of New York's 2-1 victory over the Florida Marlins on Friday night.
"On a night like tonight, when Omir Santos plays the way he has, it makes the decision easy for us," said general manager Omar Minaya, who acknowledged being surprised by the speedy progress of Santos, who was in the Yankees' organization from 2001-07, then signed with Baltimore and made it up to the majors for the first time last Sept. 5.
Broadway is 0-1 with a 5.06 ERA in eight games with the White Sox this season. Minaya said the 25-year-old right-hander will be assigned to Triple-A Buffalo and work as a starter.
Castro is owed $1,748,634 of his $2.5 million salary, and the Mets are sending the White Sox at least $1.4 million.
Castro hit .253 with three homers and 13 RBIs in 26 games this year with New York. He has 51 homers and 174 RBIs in parts of 11 major league seasons with New York and Florida, and is expected to back up A.J. Pierzynski in Chicago.
"He's going to be missed," Mets slugger Gary Sheffield said. "In the little time I got to know him he was a great teammate."
Schneider will be activated on Saturday. He hurt his back in April then injured his right calf during a rehab game in Florida. He has been on the disabled list since April 17.