Bullpens no longer work that way, if they ever did. There are no "low leverage guys." Particularly when your plan includes multiple relievers every night. Tonight was the 9th straight game where the starter did not throw a pitch past the 5th inning.
They were in a tight game yesterday. They used their best (including a clean inning from Pagan). It's impossible to navigate through even a week without needing every reliever on your staff to pitch in a close game.