"He told the world he's retiring, and that's what we thought was going to happen," Snell's agent Joe Sroba said Friday.
Sroba said further news of a potential return for Snell could come within a week, and that a return to the Cardinals, who brought him to Spring Training as a non-roster invitee, was a possibility.
Cardinals general manager John Mozeliak said the Cardinals will grant Snell his release.
Snell, a seven-year big leaguer who spent the bulk of his career with the Pirates, is 38-53 in 152 career games. The Cardinals sent Snell to Minor League camp on March 15, the day he announced his retirement.
Snell pitched in one Grapefruit League game for St. Louis this spring, allowing two runs in two innings. His best season came in 2007 with Pittsburgh, when he finished fourth in the National League in innings pitched and posted a 3.76 ERA.