To take his place on the roster, the Padres selected outfielder Jake Goebbert from Triple-A El Paso.
Goebbert's first appearance will be his big league debut. He was acquired from Oakland on May 15 along with right-hander Ronald Herrera in exchange for infielder-outfielder Kyle Blanks.
Goebbert was hitting .270 with five homers and 18 RBIs in 32 games with El Paso.
Alonso was hitting .210 with five homers and 22 RBIs.