Hernandez (elbow) thew his first bullpen session Tuesday since undergoing Tommy John surgery last March, the Arizona Republic reports. The session included 20 pitches -- all fastballs -- for Hernandez, who was accompanied by teammate Patrick Corbin. The Diamondbacks expect to have Hernandez back in mid-May, a few weeks earlier than Corbin, since Hernandez only has to stretch out to 30 pitches.