Williams was traded from the Giants to the Marlins in exchange for Hayden Cantrelle on Thursday.
Williams was designated for assignment by San Francisco last weekend, and he'll now attempt to carve out a role with a new organization. The 25-year-old has appeared in 66 games between the Phillies and Giants over the last two years, and he's hit .245 with a homer, five doubles, nine runs and nine RBI. Williams will likely report to Triple-A Jacksonville following Thursday's trade.