Boxberger, who is on the 40-man roster, had a 4.50 ERA in eight appearances this spring. He allowed four runs on seven hits in eight innings with three walks and nine strikeouts.
Valdez hit .206 with one home run and seven RBIs in 34 at-bats. Galvez hit .375 with a home run and eight RBIs in 40 at-bats.
Lopez had a 1.13 ERA in eight appearances. He allowed one run on five hits in eight innings with four walks and two strikeouts. Lopez is property of the Mexico City Red Devils and likely will return to play for them at some point.
The Padres now have 41 players in big league camp. The team breaks camp Thursday and heads to San Antonio for two exhibition games against the Rangers before moving on to Opening Day on April 1 in New York against the Mets.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.