The Nationals recalled Cornelio from Triple-A Rochester on Friday.
Cornelio earned his first promotion to the big leagues after putting up a 2.45 ERA, 1.05 WHIP and 27:8 K:BB through 18.1 innings with Rochester. The right-hander will likely be broken in as a long reliever, but given the lackluster performance of the Nationals' rotation, Cornelio could earn some starts if he pitches well.