The Mariners have drafted and developed an entire rotation in just five years

Photo by Brandon Sloter/Getty ImagesTINSTAAPP. It hasn’t quite hit the working vocabulary of baseball fans the way TOOTBLAN has, but TINSTAAPP has become axiomatic in amateur and minor-league coverage. There Is No Such Thing As A Pitching Prospect. It’s meant to capture the idea that pitching prospects flame out at a much higher rate than position players. Development is harder, injuries more common. But you say TINSTAAPP and Jerry Dipoto says, “Challenge accepted.”

Now that Emerson Hancock has made his MLB debut, the Mariners rotation this year features five starters that this regime drafted over a four-year period, developed, and turned into MLB-quality arms. That’s an entire rotation’s…