The Padres optioned Song to Triple-A El Paso on Monday.
Song was up with the big club as its 27th man during the Mexico City Series against the Diamondbacks over the weekend. He made his major-league debut as a pinch runner during Sunday's 12-7 loss but didn't receive a plate appearance. Song returns to El Paso, where he's slashed .293/.369/.320 in 20 games.