The Cardinals selected Hjerpe's (elbow) contract from Double-A Springfield on Tuesday, John Denton of MLB.com reports.
Hjerpe is expected to miss the first portion of the 2026 season after undergoing Tommy John surgery in April, but the Cardinals will grant him a 40-man spot anyway to ensure he doesn't get selected by another club during the Rule 5 Draft. The 24-year-old lefty owns a 3.38 ERA and 1.18 WHIP across his minor-league career and will presumably return to Double-A once he's deemed fully healthy.