By signing Roberto Hernandez, the Rays added to their starting rotation depth while also bolstering their bullpen. Though there is a slight chance Hernandez could see time as a starter due to a spring training or early season injury, the presence of Chris Archer and Jake Odorizzi likely destines Hernandez to the bullpen this year.
The transition from a starter to a relief pitcher is always interesting to watch. Some pitchers have a difficult time making the adjustment while others make the switch seamlessly. In recent years, Rays' fans have witnessed both Jake McGee and Wade Davis undergo a successful transition from the rotation to the bullpen. From looking at how they made the conversion, we can get an idea of how Hernandez will change.
Over the course of his career, Roberto Hernandez has thrown four different types of pitches: sinker, fastball (four seam), change up, and slider. For his career, he has thrown his sinker 51% of the time, his fastball 20% of the time, his change up 16% of the time, and his slider 12% of the time. The following chart depicts the yearly trends of his arsenal:
Fangraphs and Brooksbaseball.com differ in their distinguishing between his fastball and his sinker. I tend to trust brooksbaseball.com's individually classified data, so I will feature theirs.
Below is the velocity of the pitches during the years:
A few general trends to pick up here....
- Hernandez started his career by throwing his pitches in a similar usage as he did this past year. During the middle of his career, he used his fastball more and his sinker less.
- The velocity of his two fastballs (four seam and sinker) has decreased significantly from his first year or two of pitching. Once sitting in the mid-90's with his fastball and sinker, he now sits in the low-90s, occasionally touching 94-95.
- There appears to be no correlation between his pitch usages and success. The same can be said for his velocity. He has been hit or miss his entire career, and factors other than these probably contribute more to that.
Now for a look at each individual pitch and how he can use it in relief....
Four Seam Fastball
Once a pitch that could touch the high 90's, Hernandez's fastball has evolved into a pitch that is actually a tad bit slower than his sinker. While the fastball has more vertical movement than the sinker, it moves less horizontally.
Throughout his career, Hernandez has really struggled with his fastball. In the six years of recorded data by Brooks Baseball, hitters have teed off on his fastball, hitting .379 with a .663 slugging and a .393 TAv. He generates whiffs on only 9.70% of his fastballs, a rate below that of his other three pitches. And while his three other pitches also produce ground balls, his fastball's ground ball percentage per balls in play is only 38.33%. Even when he was throwing much harder in 2007, he still struggled to use the pitch successfully. The pitch is not exclusive to a specific handed batter either, although he throws it a little more often against left handed hitters.
Since the pitch does him few favors and is not thrown much harder than the sinker, it makes sense for the Rays to encourage him to drop the pitch in relief.
The bread and butter pitch of Hernandez's arsenal, the sinker is a pitch that has earned him the reputation of a ground ball pitcher. It lacks much vertical movement, but it moves 8.91 inches horizontally according to Pitch FX data from the last six years. It is a terrific ground ball pitch, coaxing ground balls out of hitters 64.11% of the time they put the ball in play during the six year time frame. While it is not a great strike out pitch, it still managed to generate whiffs of 14.91% of swings, which is a very solid rate.
As we saw recently with Wade Davis, pitchers add velocity when they move from the rotation to the bullpen. Their pitching stints are shorter, so they are able to air it out. Under normal circumstances, an increase is fastball velocity is expected to produce better results. But since Hernandez works with a sinker and may ditch the more traditional fastball, the rule may not apply to him. I was unsure of how his sinker reacts to increased velocity, so I decided to go through his game logs and sort the pitches by their speed.
The data goes from 2007-2012, with only a start on 5/28/2012 missing (I could not upload it from brooksbaseball.com for whatever reason). The sample size is 11,281 pitches, so it should be fairly accurate and reflective.
The chart shows that there are no conclusive trends with his results as the velocity varies. While traditional fastballs almost always are better when thrown harder, his sinker appears to be independent of a result fluctuation at varying speeds. There is a chance that his sinker will improve in the bullpen when thrown at a higher speed, but the evidence suggests that the difference will most likely be negligible.
Slider and Change up
Like most pitchers, Hernandez possesses multiple offspeed pitches to keep hitters off balance. Both the slider and change up induce a significant amount of whiffs (25.31% and and 30.05% whiff/swing respectively) with the slider used primarily against right handed hitters and the change up used as a weapon against left handed hitters. Both pitches also generate ground balls, although the change up does a much better job (65.11% versus 45.53%). Despite his success with these two pitches, Hernandez has used them only 28% of the time combined over his career, with all other pitches of the fastball or sinker variety. Pitchers as a whole used their off speed pitches 36.3% of the time last year, making his rate far below average.
The solution to finding success in Tampa Bay is not as clear as it has been in the cases of previous relief projects. The issue with Fernando Rodney was command; for Benoit, it was health; for Davis, it was velocity. However, there are several adjustments Roberto Hernandez can make to become a useful reliever. The first step is to limit or end the usage of his four seam fastball, a poor pitch that does little to complement his other pitches. To occupy that vacancy, he should, in my opinion, ramp up the usage of his slider and change up to the point where he is throwing them (combined) close to 40% of the time. If he throws the sinker 60% of the time, the change up 25% of the time, and the slider 15% of the time all while registering the same results, his TAv, in theory, should be about .247. As shown by that exercise, by simply losing the four seam fastball (career TAv of .393), he should immediately become a better pitcher.
I'll list rate stats only...
Steamer: 3.86 ERA, 3.88 FIP, 5.68 K/9, 2.44 BB/9, 0.80 HR/9
Bill James: 4.21 ERA, 4.31 FIP, 5.32 K/9, 2.81 BB/9, 0.94 HR/9
Zips: 4.62 ERA, 4.80 FIP, 5.11 K/9, 2.76 BB/9, 1.22 HR/9