Where a player bats in the order or plays on the field is not stipulated or a part of a player's contract. He didn't "decide not to play" as you've stated. Due to injuries sustained due to his occupation, he is medically unable to continue playing. That is why contracts, especially large ones, are insured by franchises. He technically isn't retired, he's medically unable to perform. If he simply retired, he would not be getting paid unless otherwise agreed upon by both parties to do so. To be legally binding, a contract only has to be agreed upon by both parties. Benefits and obligations are moot if both parties agree to it. Contracts in sports are risky for both parties by nature. The team takes the risk that the player is injured and can no longer play at the level when the contract was signed, or even at all as in this case. The team signed the contract, they're obliged to pay the remainder in this case.