Hwang burst onto the scene in June when he homered in his first game in the Majors.
Of the two relievers set to join the Giants, Law owns a better ERA. He had a 3-1 record and 5.40 ERA while with the Giants in April, May and June. Okert, meanwhile, posted a 6.75 ERA in 32 games for the Giants this season.
Federowicz joined the San Francisco organization before the season via the Cubs and appeared in two games in April when Buster Posey landed on the concussion disabled list. He slashed .300/.366/.463 this season for Triple-A Sacramento with nine home runs and 43 RBIs.
Of the four, Calixte is the player who most recently played in the Majors. He's hit .176 this season for the Giants in 34 at-bats.
Jonathan Hawthorne is a reporter for MLB.com based in the Bay Area. This story was not subject to the approval of Major League Baseball or its clubs.