The Giants designated Hjelle for assignment Wednesday.
The move is part of the Giants' trade of Tyler Rogers to the Mets in exchange for Blade Tidwell, Drew Gilbert and Jose Butto. Hjelle has pitched well with Triple-A Sacramento and has a 2.90 ERA and 1.15 WHIP across 40.1 innings, but he has failed to translate that success to the majors, where he's posted a 7.80 ERA and 2.00 WHIP over 15 innings.