Think of it this way. All major-league contracts are guaranteed until they expire. Someone has to pay the player. Another team can claim off waivers and accept the whole contract or, if the player clears waivers and doesn't return to the team (club or player choice), the original club retains responsibility for the full contract and a team that signs the player is only responsible for the minimum salary prorated for the rest of the season (and minimum salary for any remaining seasons).