Castro signed a one-year, $1.05 million contract with the Orioles on Thursday, avoiding arbitration, Mark Feinsand of MLB.com reports.
The 25-year-old appeared in 65 games last year and recorded a 4.66 ERA that was up slightly from his two previous seasons. He got the chance to record a couple saves when Mychal Givens was briefly demoted from the closer's role, but Castro will likely need to bring his ERA down if he hopes to be trusted in more high-leverage situations.