I'm going to be loose on the details, here, but I remember reading an article about the Celtics/Lakers rivalry once. Coop covered Bird, shut him down and the Lakers won the title. Bird worked all offseason on his left hand because he saw that Cooper knew that was a weakness and exploited it.
Next season, Bird got the better of Cooper and the left hand was a big part of that. Celts won the title. Cooper went on a family vacation after the finals with his family and spent the entire vacation in his hotel watching tape of how Bird beat him.
That type of stuff simply doesn't happen anymore. I know that makes me sound like "Okay Boomer" guy but it's true.