"This is positive," Cardinals general manager John Mozeliak told Hummel. "This still could put him [pitching for St. Louis] in early September."
Wacha, 23, is 5-5 this season with a 2.79 ERA, but he has not appeared in a game since June 17 -- a six-inning start against the Mets.
Joey Nowak is a reporter for MLB.com. Follow him on Twitter at @joeynowak. This story was not subject to the approval of Major League Baseball or its clubs.