In my day (the 1970s and 80s), teams carried five starting pitchers, five relievers, and any combination of 15 position players. As the 80s turned into the 90s and the 90s turned into the 2000s, the 2000s then turned into everything Sabermetric.
Billy Beane turned baseball on its collective ear in 2004 when he decided that things like on-base percentage were more important than batting average, thus opening the floodgates for teams to evaluate talent in a way like never before.
With the hiring of Andrew Friedman as President of Baseball Operations on Oct. 14, 2014, the Dodgers have embraced the forward thinking of Beane and have come as close to perfecting the art as any organization in baseball.