Hjerpe is expected to work as a piggyback pitcher behind starter Kyle Leahy in Thursday's game against the Pirates.
Since being called up from Triple-A Memphis on Sept. 6, Hjerpe has made all three of his appearances to date as part of a piggyback tandem with Leahy, whose workload the Cardinals are deliberately looking to keep in check as the season winds down. The rookie left-hander has had mixed results thus far, going 1-0 with a 12:6 K:BB while yielding six earned runs and giving up four hits across nine innings.