The principles of bullpen construction certainly have changed over the years as baseball has evolved – and from the looks of things, this year’s Pittsburgh Pirates’ pen might have even more of a revolving door look than we’ve seen in the past.
As a bit of a bullpen primer, in the early to mid-1960s major league bullpens were largely filled with failed starters and prospects deemed too raw to trust in the starting rotation, along with an actual skilled reliever or two to shut things down. Think Elroy Face.
Then in the ‘70s, teams began putting more emphasis on guys who could close out games in high-pressure – which later became high-leverage – situations.