[Danius]

Mike Clevinger is also an example, to some extent. He was a starting pitcher in the minors before joining the Indians, but he averaged less than 5 innings a start in his minors career, and it's always been assumed he'd be a bullpen guy if he made it to the majors because he didn't rate as having the stamina to be a major league starter. He's 26 now, and he's had some very impressive outings for Cleveland this year, and he's projected to be a front-to-mid rotation starter for years to come, and he might have the stuff to be an ace in the next few years. Yes, it's not exactly apples-to-apples, but if the Indians kept him in the bullpen for the next couple of years, then turned him into a starter when he was 100% ready (stamina and control maxed), he could very well go from dominant reliever to dominant starter at the flip of a switch. If needs (injuries) didn't dictate, he might not have been a starter for the Indians up to this point.

Also Chuck Finley made 85 appearances out of the bullpen in his minor and major league career over 4 years before he ever made a start in professional baseball. In his second year as a starter in 1989 (not including 3 starts in September 1987), he made the All-Star team, and finished with a 2.57 ERA and 4.9 WAR in 29 starts.