When Tommy Milone landed on the disabled list with an elbow strain over the weekend, it was Tyler Duffey who got the call to take his place. Though Jose Berrios and Trevor May were also strong candidates for the assignment, Duffey is the most logical choice at this time, and plenty deserving.



His big-league debut Wednesday night in Toronto will mark a big moment in what is shaping up to be one of the organization's most impressive developmental success stories in years.

Berrios and May have also been success stories, of course, but not quite in the same sense. The Twins spent the No. 32 overall pick in the 2012 draft to acquire Berrios, widely viewed as one of the best high school pitchers in the class. And they had to give up a quality big-league asset (Ben Revere) six months later in order to bring aboard May, who was one of the Philadelphia's more established arms in the minors.



Duffey was selected 128 picks after Berrios, in the fifth round. He had been a dominant closer at Rice University but was one of several collegiate relief arms that the Twins targeted with designs on being converted to a starter.



In most cases, that didn't pan out. In his case, it has worked out beautifully.



Duffey began transitioning into a starting role in 2013 and has been working in that capacity exclusively since the start of 2014. His results have gradually grown better and better since the switch, and that's an extremely promising sign.



Last year, his first fully committed to starting, Duffey put up a 3.68 ERA while averaging 6.8 K/9. He allowed 17 homers in 149 innings. This year, competing at the highest levels of the minors, he has a 2.66 ERA while averaging 8.0 K/9. He has allowed one home run in 132 innings.



As encouraging as the improved results are, so too is his steadily increasing workload, which suggests that his arm is responding well to the rigors of starting. Last year he made 25 starts; in the first 13, he completed seven innings only once. He made it that distance six times in his final 12 turns. This year he has already completed seven-plus frames 10 times in his 21 starts between Double-A and Triple-A.



Though the reverse path is quite common, there is a litany of hurdles involved with turning a reliever into a starter, and it's pretty rare to see it work out so well (thus, my reservations about drafting Tyler Jay sixth overall this year). But gambling on Duffey with a fifth-round pick was a savvy move for the Twins and now, just over three years later, they'll see the dividends on a major-league mound.