They wouldn't be throwing any curveballs, but they'd be changing speeds with the fastball. It all gets down to making your pitchers work efficiently. They changed speeds, kept batters off balance and threw the ball over the plate. And as a result, it took them fewer pitches to get through a given number of innings. So even though the four-man rotation has worked in the past, and experts believe it could work today, there are obstacles to be overcome if it's to be revived.
Some club just needs the courage to give it another try.