Macko will serve as the Blue Jays' opening pitcher in Friday's contest in Baltimore, Ben Nicholson-Smith of Sportsnet.ca reports.
Macko hasn't gone more than 1.1 innings or thrown more than 20 pitches in six relief outings this season, so his appearance Friday will be brief. Former Oriole Austin Voth is a top candidate to work behind in Macko in a bulk-relief role, though Toronto hasn't confirmed its pitching plans once Macko exits the contest.