Wisler is ranked by MLBPipeline.com as the Padres' No. 4 prospect.
The Padres optioned Erlin and right-handed reliever Leonel Campos to Triple-A El Paso, and they also reassigned Wisler, right-hander Jay Jackson and infielder Diego Goris to Minor League camp.
Following Sunday's 6-1 victory over the Cubs, the Padres announced that pitcher Casey Kelly had been optioned to El Paso. Kelly, working his way back from Tommy John surgery in 2013, threw one scoreless inning Saturday against Arizona. It was his first game action in 10 months.
The Padres currently have 45 players remaining in camp.
"We've got to get down to our numbers as we get closer to April," said Padres manager Bud Black, who will need to settle on 25 players by Opening Day on April 6.
Erlin had a 3.00 ERA in three games and six innings of work this spring. He threw four innings in a Minor League game on Saturday. He'll begin the season in El Paso's rotation with Wisler.
Wisler had a 14.40 ERA in three games, allowing eight earned runs in five innings.
Just because Erlin and Wisler were sent out Sunday doesn't mean the Padres have seen the last of those two this season, Black said.
"You're going to start the year with five starting pitchers in your rotation, and beyond that you know you got to feel very good who your sixth, seventh, eighth, ninth are," Black said. "And Robbie and Wis fit into that group of guys who potentially are going to be starters for us in the future."
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.