In the old days, starting pitchers and relief pitchers were one in the same. Pitchers were pitchers. When they pitched mattered little so long as they sucked it up and pitched. Even serious injuries were treated with a small application of dirt on skin.
As I'm guessing you've noticed, things are different now.
Somewhere along the way, they figured out that having designated relief pitchers was a good idea. Somewhere else along the way, they figured out that some guys are simply better suited for relief work than starting duty.
This is not to say that clubs can't change their minds about their pitchers. They're liable to transition starters into relief roles and relievers into starting roles.
Turning relievers into starters is tricky. Relievers aren't used to high pitch counts or outings that last five, six or seven innings. To boot, many of them aren't used to throwing any more than two different pitches. They are best when they're in their element, and starting is so not their element.
Teams are aware of the complications, but they experiment with their relievers anyway.
The question is whether there's any kind of discernible track record when it comes to relievers-turned-starters. Is there a trend that shows it's a bad idea? A good idea? A toss-up?
Let's go ahead and take a look. The 10 relievers-turned-starters listed ahead should serve as a telling sample group.
Note: All stats come from Baseball-Reference.com unless otherwise noted.