Gasser and Drohan both have 10 GS, 51.1 IP. That's over 5 IP/start.
Henderson not counting him being an opener in Kansas City before he was stretched out is at 6 GS, 31.1 IP. That's over 5 IP/start.
Harrison has had two injury shortened starts. If you take those out he's averaging over 5 IP per start at 15 GS, 76.2 IP