The Orioles transferred Mateo (elbow) from the 10-day injured list to the 60-day IL on Tuesday, Rich Dubroff of BaltimoreBaseball.com reports.
Mateo was placed on the 10-day injured list Thursday with a left elbow subluxation and he will now be forced to miss two months of action while recovering. He'll be eligible to return from the IL in late September if he's able to avoid any setbacks. With Mateo unavailable, top prospect Jackson Holliday is set to be called up from Triple-A Norfolk to join the major-league roster in Baltimore on Wednesday ahead of the team's series finale with the Blue Jays. Holliday will likely take over as the Orioles' primary second baseman.