"I was looking for a fastball to hit, and it happened to be on the first pitch," Peterson said after Friday's game.
Peterson, who was added to the 25-man roster from Double-A San Antonio before Friday's game, got his first Major League start at third base on Saturday against the Nationals.
Peterson -- who is filling in for Chase Headley, who landed on the disabled list with a strained right calf -- is the fourth player in franchise history to get his first Major League hit on the first pitch he saw. The others were Sean Kazmar (Aug. 13, 2008), Craig Stansberry (Aug. 25, 2007) and Humberto Quintero (Sept. 3, 2003).
Peterson went 0-for-3 in Saturday's 4-0 loss to the Nationals.
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.