Somewhere around 1978 when my Dad sat me down and explained "the baseball facts of life". I saw the Red Sox trade for Dennis Eckersley and sign Yaz to a one year contract. I didn't understand why Yaz was only signed to a one-year contract as he was a fan favorite. My Dad was an HR Exec and explained how management and labor worked with and against each other to create a market. This made sense to me at the time as I was taking high school economics. So, that is where contracts come from.....