Before a club can formally release a player, that player must first be passed through unconditional release waivers. All 29 other clubs in the Majors have the opportunity to claim the player and add him to their 40-man rosters. A player that is claimed on release waivers has the option of rejecting that claim and instead exploring the free-agent market. Release waivers are often requested after a player's contract is designated for assignment or in cases when a veteran player would otherwise refuse an outright assignment. Players are rarely claimed off release waivers, as the claiming club is required to pick up the remaining contract. Once the player clears waivers, the releasing club is responsible for the old contract.
In April 2013, the White Sox requested release waivers on left-hander Charlie Leesman, and the Rangers opted to claim Leesman. However, Leesman rejected the claim, elected free agency and quickly re-signed a new Minor League contract with the White Sox.