As Craig Wright points out in his latest newsletter (subscriber-only, but worth every penny), Earl Weaver's .583 career winning percentage is "easily the highest winning percentage of any manager in the last 50 years."
The next highest winning percentage by a manager in the last 50 years belongs to Davey Johnson (.564), who played under Earl Weaver in both the minor and major leagues. "[Earl] was as intense a competitor as I have ever met. No one managed a ballclub or a pitching staff better than Earl. He was decades ahead of his time. Not a game goes by that I don’t draw on something Earl did or said. I will miss him every day."
Would Davey Johnson be a great manager if he hadn't played for Earl Weaver? That's unknowable. But doesn't it seem quite possible that without Weaver, Davey Johnson wouldn't be heading to the Hall of Fame someday? That said, I'm a bit surprised to notice that Frank Robinson is (unless I'm missing someone) the only other notable manager who spent a significant amount of time playing for Weaver.