Zito did not pitch in 2014 after struggling to a 5.74 ERA the year prior with the Giants. He had been working out for various teams during the offseason.
The A's drafted Zito ninth overall in 1999, and he spent the first seven years of his career with the A's, winning the American League Cy Young Award in 2002. He left after the 2006 season to sign a seven-year, $126 million contract with San Francisco.
Jamal Collier is a reporter for MLB.com. Follow him on Twitter at @jamalcollier. This story was not subject to the approval of Major League Baseball or its clubs.