The Orioles designated Walker for assignment Friday, Roch Kubatko of MASNSports.com reports.
Walker was claimed off waivers from Atlanta earlier this month after he was previously DFA'd by Baltimore in November. He's now going to be exposed to waivers once again. The 31-year-old left-hander appeared in three games for Toronto last season, turning in a 7.20 ERA, 2.00 WHIP and 8:2 K:BB across five innings of work at the big-league level.