While Contreras will be used out of the bullpen initially, the team will keep him on close to a starter's schedule and try to use him for multiple innings as he gets stretched out, Justice delos Santos of MLB.com reports.
Contreras is arguably the most talented pitcher on the active roster, so he will eventually join the rotation, but the Pirates were going to have to monitor his innings regardless, so starting him off in a multi-inning relief role while keeping him on a starter's schedule makes sense. While his future is bright, we shouldn't assume the Pirates will keep him up in the majors all season.