The White Sox agreed to a major-league contract with Slater on Monday, Jon Heyman of the New York Post reports.
Slater is absent from the lineup Tuesday in Game 1 of the American League Wild Card Series against the Royals, Roch Kubatko of MASNSports.com reports.
Slater went 1-for-3 with a two-run homer in Wednesday's 4-3 loss to the Mets.
Slater was traded from the Reds to the Orioles on Tuesday along with Livan Soto in exchange for cash, Mark Sheldon of MLB.com reports.
Slater started in right field and went 1-for-4 with two RBI and a run scored in Friday's 8-5 loss to the Nationals.
Slater started in center field and went 1-for-3 in Wednesday's 6-5 loss to Colorado.
Slater won't be available to make his Reds debut until Tuesday's game against the Rockies, C. Trent Rosecrans of The Athletic reports.
Slater isn't in the Giants' lineup for Wednesday's game against the Cubs, Susan Slusser of the San Francisco Chronicle reports.
Slater isn't in the Giants' lineup for Tuesday's game against the Cubs, Shayna Rubin of the San Francisco Chronicle reports.
The Giants reinstated Slater (concussion) from the 7-day injured list Wednesday. He'll start in center field and bat leadoff in the Giants' series finale versus the Diamondbacks.