Strikeout Rate Risers and Fallers for Week 9

Strikeout rate risers and fallers based on RotoBaller's premium tool. Matt Williams identifies some starting pitchers (SP) whose changes in K rate could make them worth adding or dropping in fantasy baseball leagues.

Due to a combination of harder throwers and hitters focusing on hitting for power, strikeouts are at an all-time high in baseball. For pitchers, this is an ideal trend. The ability to generate swings and misses is the most important skill to possess, as it's the only true way to control what happens after the pitch is thrown and eliminate the randomness that the ballpark, fielders, weather, and luck can play.

The stat is equally important for fantasy players. Not only are strikeouts a category in every league, but K-rates are often indicative of overall production. A pitcher with a 4.50 ERA with a 25.0 K% may see some positive regression in the future. On the other hand, a hurler with a 3.00 ERA and 16.0 K% may not see the ball continue to bounce their way.

In this column, we'll review two strikeout rate risers and fallers to determine if their performance will improve, hold steady, or worsen as the season moves along.

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Risers

Michael Fulmer, Detroit Tigers

2017 K-Rate: 16.9%; 2018 K-Rate: 21.2%; Last 30 Days: 27.0%

Michael Fulmer had a breakout rookie campaign in 2016 that saw him go 11-7 with a 3.06 ERA and a 20.4% strikeout percentage. Fantasy owners were excited for the Detroit righties sophomore campaign hoping for a repeat performance. Sadly for them, it did not go that way. The 2017 season actually began rather successfully for Fulmer who owned a 3.20 ERA and 1.10 WHIP through his first 16 starts. Then the wheels started to come off. Fulmer dramatically decreased the use of his four-seam fastball, mixing it in just 22.41% of the time compared to 37.13% in his rookie season.  The Tigers right-hander also stopped throwing as many sliders, which my have been caused by an annoying elbow injury that derailed the rest of his season. Fulmer finished 2017 with a 3.83 ERA and a disappointing 16.9% strikeout percentage. The Tigers ace ended up needing surgery to repair the ulnar nerve in his elbow, which he had during the offseason.

The six foot, three inch, 210-pound pitcher was poised to pick up where he left off in 2016, full recovered from elbow surgery and ready to work during Spring Training. Fulmer came into the year with both motivation to return to form and armed with a plan to execute it. He started the plan but forcing his slider into the rotation far more often, increasing his usage from 21.08% to 27.27% (chart below). This change was more in line with his breakout rookie campaign in 2016 and had a positive impact on his overall effectiveness, which even to led to an amazing game on April 26 in Pittsburgh when he got ten swings and misses on his slider alone.

So what was the big change in the last 30 days that led to such a drastic increase to his strikeout numbers? It was not the slider, which still remained a primary weapon in Fulmer's arsenal. The change came in the form of a complete overhaul of his fastball approach. The month of May showed that the Tigers new game plan was to dramatically alter the usage of their right-handers four-seam fastball and his sinker. I am not exaggerating when I say that Fulmer threw over twice as many four-seam fastballs over the last 30 days, while also cutting the use of his sinker by 25 percent.

The new approach led to an increase in the whiff rate on both pitches , even the sinker. In two different starts in May, Fulmer was able to dominate a start using his four-seam fastball. On May 7 in Texas, the right-hander was able to pile up eight swing and misses on the fastball, while collecting another 10 in his May 18 start against the Mariners. Fulmer is still continuing to have success with the overall increase in his slider usage but seems to have found the magic combination to make his pitches their most effective. Unfortunately, Fulmer has also seen an increase in his walk rate over the last 30 days which has stunted his success. Even so, if the Tigers ace can manage to keep down the base runners while maintaining his new aggressive approach he could be in a special second half this season.

Tyler Skaggs, Los Angeles Angels of Anaheim

2017 K-Rate: 20.8%; 2018 K-Rate: 24.5%; Last 30 Days: 30.2%

Tyler Skaggs in a curious case for this article. The Angels left-hander is having a solid season, holding a 3.11 ERA, 3.65 FIP, and a 9.65 K/9. Month-to month Skaggs has not seemed to make a noticeable change to his approach that would lead to a big change in his strikeout percentage. The Los Angeles righty did increase the use of his sinker over the past month, but it has not impacted the effectiveness of the offering. The change we are looking for comes in the form of pure movement. Skaggs has managed to get a solid increase in the vertical movement of his pitches over the month of May, with the most notable difference coming on the change-up. This movement seemed to move the needle on his whiff percentage for each of his pitches, with the change-up again being the most noticeable. Skaggs was able to pick up an additional five percent swing and miss on the change-up while also making small gains on his curveball. The cart below gives you an idea of the subtle, but definite rise in the movement on all of Skaggs pitches in the month of May.

It is not all good news though for the Angels right-hander. The increase in movement and subsequent increase in strikeouts has come at a cost. Every single one of Skaggs pitches have become easier to square up. You heard me correctly. Every single pitch he has thrown has become easier for the opposition to hit from month to month. Don't believe me? Look at the chart.

So yes, Tyler Skaggs has increased his strikeout percentage over the last month. It sure has not helped him pitch better. Skaggs 2.95 FIP and 8.82 K/9 from April has increased to a 4.67 FIP and 10.88 K/9 in May. You win some, you lose some. Some of the damage has been caused by an inflated .346 BABIP, but on the other hand, Skaggs has been aided by a 96% strand rate. It is hard to gauge where the bad luck ends and good luck begins with guy. One thing that seems to make the most sense is that Skaggs has been the victim of getting taken deep over the last 30 days with a 2.01 HR/9, that will make your numbers take a serious hit. In true Skaggs fashion, this can be reasoned away with an unreasonably high 22.7% HR/FB ratio that is all but certain to fall back to earth. The bottom line here is that Tyler Skaggs is having a fine season, highlighted by a an increased strikeout rate. Are there concerns? Absolutely. However, there are too many variables and signs of bad luck to make a reasonable conclusion for the sudden change in pitch effectiveness.

Fallers

Steven Matz, New York Mets

2017 K-Rate: 16.1%; 2018 K-Rate: 21.4%; Last 30 Days: 14.9%

Mets' southpaw Steven Matz has always had ace upside. The problem so far is his career has been hi ability to stay injured consistently. This has caused Matz to lose momentum and change his approach on numerous occasions. In fact, the left-hander refused to even throw a slider in April due to fear of the pitch causing an injury. On the surface it seems as if Matz had recovered from a difficult 2017 campaign that saw him compile a 6.08 ERA and a 16.1% strikeout rate. So far this season Matz is carrying a solid 3.80 ERA to go with an improved 21.4% K rate. The success is a bit of fools gold if you look at the southpaws 5.63 FIP over nine starts.

Over the past 30 days Matz has seen a steep decline his strikeouts, dropping from a 10.8 K/9 in April to a 5.57 K/9 in May. Even though Matz started throwing his slider again over the last 30 days, his overall strikeout total has seen a decrease due to the ineffectiveness of this other breaking pitches. The lefty has thrown over five percent more change-ups while throwing almost half as many curveballs. The problem with throwing more changeups is that the overexposure of the pitch has led Matz fooling less batters.

There has been no significant velocity change to explain the change in pitch effectiveness, not has their been a significant change to overall movement. The best explanation is reintroduction of the slider. Matz' 84 MPH changeup can be an effective pitch when mixed in against his 94 MPG fastball. However, if you mix in an 88 MPH slider the speed differential takes a drastic hit if the pitch sequence is not balanced correctly. It's enitrely possible that hitters are just not being fooled by the offspeed pitches as much in May due to the lack of variance in the speeds being offered.

You can see in the above chart the problem that introducing a pitch which fills the gap between the fastball and changeup can be. You take the biggest weapon a change up has, which is the ability to get a hitter off balance, and you take that away by lowering the range in which the batter needs to adjust. The slider is a dangerous weapon that Matz should certainly to try utilize going forward, but it looks like in the last 30 days batters have had an easier task timing Matz due to the lack of parody in the speeds offered at the plate.

Patrick Corbin, Arizona Diamondbacks

2017 K-Rate: 21.6%; 2018 K-Rate: 32.7%; Last 30 Days: 27.2%

A popular preseason sleeper, Patrick Corbin got off to as hot of a start as you could imagine this season. The right-hander carried a 1.96 xFIP and 36.7% strikeout percentage in April leading many to believe that this was a true superstar breakout we were witnessing. On the season Corbin still holds a 2.47 ERA and 3.02 FIP to go with a 32.7% K rate but has seen his strikeout total take  hit over the last 30 days. Let's take a look at what could be the problem.

The easy culprit to point to here may also be the answer: pitch velocity. Corbin has seen an overall decrease in his fastball velocity by almost three miles-per-hour, while also seeing a dip in his sinker (no pun intended). Oddly enough Corbin has retained the same speed on his breaking pitches, even picking up a tick on his changeup. It should not be a surprise that a velocity issue would lead to problems, just look at literally everyone it happens to for that matter.

It should also come as no surprise that the velocity dip has had a negative impact on Corbin's ability to fool hitters. The same as Steven Matz, if your pitches all seem to be coming in at the same speed it's easier for the batter to stay balanced and make contact. Corbin has seen close to a 50% drop in his whiff rate on his four-seam fast ball in May while seeing the same negative results on his sinker, curveball, and slider.

Patrick Corbin has still been an effective pitcher in May, just not the same kind of pitcher. He holds a 3.51 FIP and is holding opposing batters to a .198 batting average. The main change to Corbin's game is how the loss of velocity has impacted how he gets his outs. Hitters are not being fooled as much anymore and are making contact. So, instead of heading back to the dugout after a strikeout, opposing hitters are heading back to the dugout after hitting a flyball. There are a couple of red flags that come with the extra contact hitters are making. The obvious one is that batted balls can fall for hits and strikeouts can not. This is a simple but valid point. The real worry here is the kind of contact being made. In May, Corbin has see his hard-contact rate increase from 33.7% to a worrisome 49.3% while seeing his ground ball rate drop nearly 10% as well. The bottom line here is that while Corbin's ERA may be closer to the 3.67 xFIP he is sporting in May instead of the superstar we saw in April, he is still a very serviceable fantasy player that should remain valuable.   The expression "an out is an out" may be fine for the Diamondbacks manager, but fantasy owners sure would like to see some strikeouts. I'm not sure they are going to come back if Corbin fails to locate where his lost velocity is hiding, but he should remain a solid option in mixed leagues in 2018 regardless.

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