Helsley was recalled from Triple-A Memphis on Wednesday.
The Cardinals will need someone to fill Genesis Cabrera's spot in the rotation after the latter was optioned in a corresponding move. However, that's unlikely to be Helsley, who's in the midst of transitioning to full-time reliever. Helsley owns a 3.38 ERA in eight innings of relief for the Cardinals this season, and a 3.86 ERA in the 23.1 innings he's logged for the Redbirds.