Guaranteed Sports Contracts

I need help from my fellow clutchfans. With the whole "Ben Wallace retiring situation" I got into a debate with my co-worker about guaranteed contracts. He believe that any player, while in a guaranteed contract, could retire and get paid no matter what. He thinks teams would buy out any players contract, anytime.

To make my point, I suggested that if Lebron wanted to retire this summer, that the Cavs would not have to pay him for next season. I believe the Cavs would make him stay on the team (bench) and pay him his full contract, or he could leave and not have to pay him anything. He believes that the Cavs would eventually just buy out his contract for about 70-80% of its value.

Am i correct here???? I believe the only way a buyout works is if both player and team decide they dont want the player to play.

Has there ever been players who have retired and have walked away from their guaranteed contracts?