After making the team out of spring training, Chasen Shreve's Yankee career is off to an interesting start. He has a 1.59 ERA and 3.23 FIP with a 9.53 K/9 without allowing a walk in 5.2 innings over just three games. If you remember, he managed to provide 3.1 innings of relief during that 19-inning affair with the Red Sox and it made some people start to wonder if maybe he could be stretched out as a starter. The Yankees haven't made the move yet, but could they?
The Yankees have done this before with Chase Whitley, and they're still doing it now with Taylor Garrison being the latest to make the conversion in the minors. Whitley was an intriguing reliever who was lost in the shuffle, but they gave him a chance to start and he turned out to be a lot more valuable than anyone realized. When Shreve was sent to Triple-A after that impressive appearance in order to get a fresh arm up it would have been the perfect opportunity to start experimenting with him, however they recalled him as soon as he was eligible again. During that time he only made one appearance, but it was a 2.1-inning outing, making it seem that the transition could be possible. Turn those three-inning appearances into four and then five innings and suddenly the Yankees have another viable starter.
He certainly seems capable of taking on the workload. The Braves didn't use him for more than two innings, but at one point in his minor league career he was shaping up to be a real workhorse. He was a starter in college and back in rookie ball and Low-A, Shreve averaged 2.0 innings per appearance. As he moved up through the system, he went to 1.5 innings in High-A and then 1.0 innings in Double-A and Triple-A. It's easy to experiment with players when they're young and far from the majors, but the Braves likely saw potential in him and wanted to develop him as a traditional reliever in order to help the big league team and so he had shorter and shorter outings. With a history of a higher innings threshold and no recent injury history, Shreve could probably take on the physical demands of a starting pitcher.
When discussing how his stuff would play up as a starter, the conversation really starts with velocity. For awhile Shreve only pitched in the high-80s and would maybe hit 90, however, he was apparently holding back in order to focus on his control. In 2014, he saw his velocity jump from 86-90 to 91-95 before settling at 93-94. The jump is what made the Braves call him up, though in his short time in the majors, his fastball velocity is still averaging only about 91 mph and so far he has only topped out at 93, so it's unknown if that 94-95 is still there.
Aside from the workload and velocity, Shreve would have to have the pitching repertoire to make it as a starter. He is mainly a fastball–slider guy, but also has a changeup he can throw. In 2014 he also threw a two-seamer and a curveball, but he has yet to use either in 2015. After being converted into a starter, Chase Whitley threw fastball-slider-change with a two-seamer also mixed in there, so Shreve would have to expand his pitch selection to more than two pitches and the conversion would likely rest on the success of his changeup.
Whitley averages about 90 mph on his fastball and tops out at 93, but he also has a strong changeup (23.2% swinging strike rate). Shreve relies on his slider (20.7% swinging strike rate in 2015) so it's no surprise that the Yankees liked Shreve as a fastball-slider, high-strikeout reliever. The trouble with that pitch selection is that it limits the amount of weapons he has if he ever gets a shot as a starter. Whitley has two decent secondary offerings with the changeup and slider, giving him the ability to change things up on the hitter. As good as a pitcher may be with two pitches, eventually, over a long enough outing as a starter, hitters will start to catch on to his offerings and sit on the fastball. Neither Whitley or Shreve have overpowering or very missable fastballs (5% and 8.9% whiff-rate, respectively), so their secondary stuff needs to be working in order to miss bats and generate ground balls. That's how it would all come down to the changeup.
In the end, it would seem that he has the stamina, but not the stuff. As much as he might be able to handle the added workload, Shreve likely doesn't have the weapons to make it as a starting pitcher. He would be extremely valuable as a left-handed starter with a strikeout slider, but his velocity and pitch selection would be a concern. If he were to move into the rotation, his velocity would surely drop and if he's averaging only 91 mph in the bullpen, a high-80s fastball is going to get hit. The Yankees first need to know whether Shreve still has that 95-mph fastball in him or not. They also need to know how effective the changeup can be because he would need a third pitch, and it would likely need to be a strong offering with how unimpressive his fastball currently is.
The Yankees have the bullpen depth this year to replace Shreve if they want to experiment and see what he's capable of. The conversion might not work like it did with Whitley, but it's certainly worth a shot. The more likely scenario is that he could serve as a long reliever capable of going four or five innings if the team is in a bind. Those three-inning shutdown performances are also pretty nice to have, though, so no matter what ends up happening, his ability to provide multiple innings of work will be key.