The Giants have released Jose Casilla according to Henry Schulman of The San Francisco Chronicle (Twitter links). The move frees up a 40-man roster spot for Waldis Joaquin, who could have opted out of his minor league contract had he not been added to the roster.
Casilla, 22, is the brother of Giants reliever Santiago Casilla. He had a 9.49 ERA in 12 1/3 innings for San Francisco's Single-A affiliate, and Schulman notes that he is recovering from Tommy John surgery. The team could opt to re-sign him to a minor league contract.
Joaquin, 24, has pitched to a 3.79 ERA in 35 2/3 relief innings for the Giants' Triple-A club, though he's walked nearly as many batters as he's struck out (18 to 17). He's made appearances for the Giants in each of the last two seasons, allowing 11 runs in 15 1/3 innings.