Dennick's numbers, along with the strong seasons so far from other starters, sent me to check out the ERA leaders among farmhands who have thrown at least 33 innings (just seemed like the proper cutoff). Of course, this precludes Cingrani's 0.00:

Chad Rogers (51.1) . . 1.93
Armando Galarraga (44) . . . 2.66
Ryan Dennick (51) . . . 2.82
Greg Reynolds (56.1) . . . 2.88
Tim Crabbe (50) . . . 2.88
Carlos Contreras (47.0) . . . 3.23*
Drew Cisco (55.2) . . . 3.40
Josh Smith (46.2) . . . 3.66
Sal Romano (41.1) . . . 3.70
Chad Reineke (48.2) . . . 3.88
Robert Stephenson (47) . . . 4.02

* Contreras is pitching in Bakersfield. You get extra credit for that.