Should Danny Duffy be a starter or reliever?

Last season, the Royals used ten different starting pitchers, nine of whom made at least four starts. Depth is key to any starting rotation, which is why the Royals have stockpiled arms this winter. Yordano Ventura, Edinson Volquez, and Ian Kennedy are locks to be in the rotation. That leaves the remaining two spots to be filled by a pair from the following - Kris Medlen, Danny Duffy, Chris Young, Dillon Gee, Chien Ming Wang, and Kyle Zimmer, plus any other pitchers they add before Opening Day. Most likely the competition will come down to Medlen, Duffy, or Young, with many observers feeling that Duffy could be sent to the bullpen. But is that the right choice?

Danny Duffy has shown flashes of brilliance interspersed with waves of frustration since returning from Tommy John surgery in 2013. In 310 innings since returning, he has produced a very productive 3.16 ERA in parts of three seasons. However, the knock on Duffy is that he has trouble finishing what he started. In 54 starts the past three seasons, he has made it through six innings just 29 times (53.7%). Overall, Royals starting pitchers went at least six innings 65.8% of the time over the last three seasons combined.

Let's see how Duffy stacks up against his competition. Here are their numbers the last two seasons, just as a starting pitcher.

This is a bit unfair to Kris Medlen, since he had a small sample size of just eight starts and was returning from his own Tommy John surgery. Certainly he has the potential to do much better, such as he did in 2013, when he won 15 games with a 3.11 ERA and 3.48 FIP with 7.2 strikeouts-per nine innings and well over six innings per start. But Duffy does stack up favorably to Chris Young, who has pitched well the last two seasons and was clutch for the Royals last post-season.

For comparison, here is how those starting rotation candidates compare to the three "locks" of the rotation.

Some have argued that Duffy should move to the bullpen not because of his deficiencies as a starter, but because of his potential as a reliever. The rationale of moving any pitcher to the bullpen is that in a shorter stint, they can get amped up and throw harder. This is how Wade Davis went from crummy starting pitcher to the Gatekeeper to Hades coming out of the bullpen.

Indeed, this has been true for Danny Duffy as well. In April of 2014, he averaged 96.5 mph on his fastball as a reliever. When he joined the rotation, that velocity dropped to 94.0. Some of that may be him wearing down over the course of a season, particularly after he suffered a rib injury late in the year. However in 2015, he began in the rotation and averaged 94.3 mph on his fastball. When he moved into the bullpen in September, his velocity jumped again to 95.6 mph.

Of course, Kris Medlen and Chris Young have relieved as well, with pretty decent results to boot. Again, here are their numbers over the last two seasons.

It shouldn't be a surprise that most starting pitchers became much more effective coming out of the pen. In Duffy's case, not only is he racking up more strikeouts, but he's inducing more ground balls. He's also allowing less hard contact, although there is the caveat that he's thrown less than 300 pitches as a reliever, so small sample size limitations apply.

What should be kept in mind however is that a good starting pitcher is more valuable than a good reliever any day of the week. If Danny Duffy can still serve as a good starting pitcher, he should be given that chance, even if he has the potential to be a good reliever as well. However, if the Royals feel Duffy's inconsistencies are too worrying for a contending team, his value as a reliever is what will keep him on this roster.

The positive going into spring training is that the Royals will have options, and they will actually be good options, not like the time they decided whether to start Runelvys Hernandez over Jeremy Affeldt on Opening Day due to a coin flip. There is not a lot of daylight between Danny Duffy and his competitors both as starting pitchers or as relievers. Most likely the decision will come down to things the numbers can't quite reveal to outside observers. Danny Duffy has been told to prepare as a starting pitcher. He has shown a lot of potential as a pitcher, but he stands at a crossroads this spring, and he will need to fight to keep a spot in the rotation.