Kelvin Herrera, Starting Pitcher?

With the Royals hurting for starting pitching, Sam Mellinger sent out this tweet a few days ago:

The idea of a moving a closer to be a starter has been contemplated by the Royals and their fans over the last few seasons with the likes of Joakim Soria and Aaron Crow. Other teams have had success with the transition with such pitchers as C.J. Wilson and Chris Sale making the move. While Soria was never tried as a starter and the Crow experiment was shut down during spring training, could moving Herrera to be a starter work for the Royals?

Kelvin Herrera started his career has a starter. From 2007 to 2010 (age 17 to 20), he appeared in 34 games and started 23 of them. During those seasons, he had a 2.07 ERA, K/9 of 8.4 and a BB/9 of 2.2. The main problem for him over those 4 seasons is he made only 8.5 appearances per season. He was on the DL for several injuries to his right elbow. Here are the number of innings he pitched each season:

2007: 42
2008: 63
2009: 5
2010: 41

In 2011, he was moved from being a starter to the bullpen where he put up an 1.60 ERA, 9.3 K/9 and 2.0 BB/9 on 3 different teams while moving through the minors. He has thrived since making the move to the bullpen.

Even though he is throwing in the bullpen, injuries with still be a concern with him for several reasons. First, he has a history of elbow issues and they may return. Second is that he throws hard. Currently he has the highest average fastball velocity in the majors at 99 MPH. More speed leads to more stress which leads to stuff breaking. Third, he doesn't have the biggest frame for a pitcher standing at 5'10". Smaller body means smaller tears in muscles and ligaments becoming a bigger deal. Finally, some people suggest that his mechanics are not the best for a pitcher to stay healthy.

While Herrera may have problems staying healthy as a starter, could he be productive as one? A key for a pitcher to make it as a starter is that they need to get both right and left-handed hitters out. Sadly, I only have his 2012 handedness data (MLB), so the values should be taken with a grain of salt. Here are the numbers:

vs LHH
K/9: 8.2
BB/9: 2.4
HR/9: 2.4

vs RHH
K/9: 7.8
BB/9: 1.2
HR/9: 1.2

His stats against right and left-handed hitters are generally the same this year except for the home run allowed. A pitcher's strikeout and walk rates stabilize quicker than HRs allowed, so those two rates are closer to his true talent level. I would have confidence, right now, that he can get out both handed hitters.

One problem he will see is a drop in velocity when moving from the bullpen to being a starter. Here are some pitchers that recently made the transition from closer to starter.

Chris Sale
Before: 94.9 MPH
After: 90.8 MPH

C.J. Wilson
Before: 93.4 MPH
After: 90.4 MPH

Neftali Feliz
Before: 96.3 MPH
After: 94.7 MPH

Daniel Bard
Before: 97.3 MPH
After: 93.3 MPH

The average drop in MPH for these 4 was over 3 MPH (3.2). Historically, some researchers have the drop closer to 1.5 to 2 MPH. His fastball would probably end up being near Paulino's average of 96 MPH.

For his production, he would expect to see an increase in is ERA/FIP of 1.0 above the level he is projected to have as a reliever. Using various projections, his ERA/FIP as a starter would project to be between 3.25 to 5.35. This is quite a range for him. The values go from being a staff ace to worse than Mendoza. The problem with projecting him is that there is not much data currently available on him. A way to get an idea of his true talent level is to compare him to other pitchers.

To get an idea of similar pitcher, the pitcher comparison values at BrooksBaseball.net can be used. The value are calculated by looking at similarities in pitch types, speed and break between various pitchers. Just 5 names are given. Also, the best scores found for all pitchers are around 90, so the values for Herrera show fairly similar pitchers. Here are the 5 pitchers that are the most similar with their scores (smaller number means more similar):

Pitcher: Score
Brad Peacock: 185
Anthony Varvaro: 189
David Robertson: 282
Brian Broderick: 340
Julio Teheran: 450

Kelvin is basically a 3 pitch pitcher with a fastball, curve and change. These 5 pitchers throw the same 3 pitches. Peacock and Teheran are both highly ranked prospects (Teheran 5th overall, Peacock 41st overall by Baseball America in 2011), but have not yet seen success at the major league level in a few starts for each pitcher. Varvaro (can't stop walking people - 5.5 BB/9) and Broderick (can't strike anyone out - 2.9 K/9) have both been used sparingly as relievers in the majors. The one pitcher with a few season under his belt is David Robertson and his career 4.7 K/BB and 3.00 ERA. These 5 pitchers don't all fit into one mold. Herrera stuff is though close to that of a top prospect and reliever in the game. If they have the ability to succeed on the 3 pitches, he could also with the right guidance.

By taking all the information together, I think Herrera has the ability to make it as a starter in the majors. He could actually be a pretty decent one. His main problem will be if his right elbow can hold out. The Royals just lost their injury prone, slightly bit All-Star closer for the season with his second Tommy John surgery. I just don't think Herrera could hold up as a starter for an entire season. I think he should stay in the bullpen and the team and fans should be happy with as much production as they can get out of him over the next few years.

H/t to RoyalsRetro for pointing out the tweet to me.