Coming into this season, most Rays fans set low expectations for Roberto Hernandez. We hoped he would eat innings in the fifth starter role, even if the quality of this innings left something to be desired. Most anticipated meager strikeout totals, an average amount of walks, tons of ground balls, and not many balls clearing the fences. In other words, we expected Hernandez to be his own typical self.
So far, Hernandez's season has been.... different. He is not working as deep into games as one would like, and while he is generating ground balls, he is also surrendering an alarming amount of home runs. Even more surprising is that his strikeout rate has exploded (8.04/9 compared to 5.54/9 in his career). While neither his ERA nor his FIP paints a pretty picture of his season, both xFIP and SIERA, two of the most popular ERA estimators, believe that he has been unlucky and could be in the midst of a career year.
On the surface, the reasoning for the optimism is very solid. His strikeout rate has climbed to a very good level, his walks are more than under control, and he is inducing ground balls. SIERA, which takes into account a pitcher's batted ball profile (fly balls, line drives, and ground balls), estimates his true ERA to be 3.46. Meanwhile, xFIP, a version of FIP that normalizes HR/FB% to 10.5%, agrees with SIERA; his xFIP this year is 3.48. The strong peripherals are leading stat-inclined fans and analysts to expect regression; the idea is that when Hernandez's 22.0% HR/FB rate reaches normal levels, he will be fine.
So, in other words, we are supposed to wait for his home run numbers to regress. His high home run rate is not a true indication of his talent. But I suggest we ask ourselves another question: are these strikeout and walks an indication of his true talent level? It seems like faulty analysis, in my opinion, to overlook the fact that his current strikeout and walk rates could be a misrepresentation of how he will pitch going forward.
On the surface, Hernandez's higher strikeout rates appear reasonable. He is now under the tutelage of Jim Hickey, wildly regarded as one of the best pitching coaches in the majors. He is throwing fewer fastballs and far more change-ups. There are several other explanations that also feed this narrative. Still, I decided to take a closer look at the numbers.
Here is a comparison of the Roberto Hernandez's plate discipline statistics both this year and his last good year, 2007.
A few things immediately stand out. Hernandez has nearly an identical swinging strike rate as he did in 2007, but his strikeout rate is much higher this year. Hernandez is throwing far fewer pitches in the zone (Zone%), and more hitters are swinging at pitches outside of the zone. This appears to be a result of him throwing his change-up much more often as a chase pitch. However, interestingly enough, hitters are making much more contact on pitches outside of the zone. On the other hand, hitters are swinging at less pitches in the zone, though they are making similar levels of contact. Overall, hitters are swinging less.
What does all this mean? Hernandez is throwing less pitches in the zone, and batters are swinging less often. However, they are swinging much more frequently at pitches outside of the zone, which should lead to an increased strikeout rate. Since they are making more contact on these pitches, both his contact and his swinging strike rates are very similar. While these plate discipline stats indicate a change, they do not particularly suggest that his strikeout rate should be higher.
K% and SwStr%
For two years, we, as Rays fans, were mystified by how Jeremy Hellickson struck out so few batters despite generating so many swings and misses. As Bradley Woodrum illustrated, swinging strikes correlate well with strikeouts. Pitchers that get lots of whiffs tend to get lots of strikeouts. For whatever reason, Hellickson was a very rare exception, receiving lots of whiffs yet not many strikeouts.
The whole idea of whiffs correlating to strikeouts takes us back to Roberto Hernandez. Hernandez features the 21st best strikeout rate in the AL (K%) and the 28th best swinging strike rate. Since Hernandez's swinging strike rate is 8.5%, I looked at all qualified AL starting pitchers with a swinging strike rate from 8.0% to 9.0% to see how their K% compared to Hernandez's.
Twelve pitchers fit this profile. As a group, they combined for a 8.5% swinging strike rate, which is exactly the same as Hernandez's. Their strikeout percentage was 20.6%, 0.2% higher than Roberto Hernandez's. This proposes that Roberto Hernandez's strikeout rate, based on his swinging strikeout rate, is right around where it should be.
This leaves us in a bit of a quandary. For his career, Roberto Hernandez has always been on the lower end of the strikeout range for a pitcher with his swinging strike rate. 2007 is a perfect example of this, as his SwStr% was nearly the same as this year's yet his K% was much lower (see the above chart). However, he has made several adjustments this year (more change ups, and more inside sinkers) that could possibly explain his higher strikeout rate. Additionally, his strikeout rate is now in the proper range compared to his SwStr%.
So what should Hernandez's K% be going forward if he continues to pitch the way he has this year? Personally, I think the answer is somewhere in the middle. Because of his career numbers, I think the K% will dip a little; however, I believe the adjustments truly made a difference and that his strikeout rate will be better than it was in 2007. If I had to pick a certain percentage, I would peg his K% going forward at around 18.5%.
Much has been made of Hernandez's strikeout rate while his stellar walk rate is overlooked. Hernandez is walking only 6.2% of batters he is facing, down significantly from his career rate of 8.7%. While it is debatable whether his strikeout rate will regress, there is convincing evidence that his walk rate will worsen.
For his career, Hernandez has thrown balls 38% of the time. This year, he is throwing balls 36% of the time, which is slightly less. However, as I already pointed out, his walk rate is down significantly from his career percentages, not slightly. Additionally, there is nothing in his plate discipline profile that explains the decrease in walks. If batters were making more contact and putting balls in play early in the count, a lower amount of walks would make sense. However, his contact percentage, which is the percentage of time a batter makes contact when swinging, is actually lower than his career averages. When batters are swinging, they are putting the ball in play 42% of the time, only one percent down from his career.
I believe it is safe to assume that Hernandez's sparkling walk rate will closely resemble his career figures for the remainder of the season.
While Hernandez may not be as bad as his ERA says, there is evidence that both xFIP and SIERA also overrate his value. My guess is that Hernandez, going forward, will see his home runs and strikeouts dip, while also seeing his walks increase. A pitcher with a HR/FB% of 12%, a 18.5% strikeout rate, and a 8.7% walk rate is about a 3.85 FIP pitcher. Since Roberto Hernandez is on pace to pitch around 180 innings, that makes him about a 2.7 WAR pitcher if the FIP is extrapolated over the course of a 180 inning season. If he pitches his remaining 21 or so games at a 3.85 FIP level, he should total about 2 WAR on this year.
That is a very good rate for a team's fifth starter, and most certainly more than we expected heading into this year. The question to me though is this: is it worth keeping a short term option in the rotation when some of the younger arms are waiting for a real chance in the major leagues? When Chris Archer comes back, the Rays will have a tough decision to make. Do they send down Chris Archer, who deserves a shot at starting in the major leagues? Since Alex Torres is out of options, when will he get an opportunity to start in the major leagues? Roberto Hernandez might be a slightly better option than these two going forward, but is it worth keeping him in the rotation instead of letting the young pitchers prove their worth in the majors? Should the Rays gain a few runs now potentially at the expense of the future? And, most importantly, will Roberto Hernandez maintain his improvements? It is certainly a worthy discussion with both sides possessing arguments of merit.