"It's time for Robbie to get another start, and we'll see where we go from there," Padres manager Bud Black said. "We've got to see what guys can do at this level."
Erlin, 22, is 1-2 in six games, including four starts, with the Padres. His most recent start came July 7 against the Nationals, and he allowed nine earned runs in four innings.
Erlin, rated the Padres' No. 15 prospect by MLB.com, was 8-3 with a 5.07 ERA in 20 starts with Triple-A Tucson, though he was 2-0 with a 4.71 ERA over four starts this month.
"In Robbie's first four starts, two have been good; two have been a little rough," Black said. "It's time for Robbie to make a statement as a Major League pitcher."
Black said some consideration was made to have Tim Stauffer make a spot start but that the team wanted to give Erlin an extended look moving into the final month of the regular season.
The Padres will most likely look at other younger pitchers in September, like 23-year-old right-hander Burch Smith, who is 5-1 with a 3.83 ERA in 11 starts with Tucson. Smith, the organization's No. 9 prospect, was up with the Padres earlier in the season, posting an 11.37 ERA in six games, including three starts.
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.