Strikeout Rate Risers and Fallers - Buy or Sell for Week 2

Welcome to the first edition of pitching strikeout rate risers and fallers this season! As fantasy players and analysts, we have many different advanced stats at our disposal, but some are more helpful than others for fantasy purposes. One of the more useful stats for analyzing pitchers is K%. Strikeout percentage holds direct fantasy value in both points and categories leagues, so staying on top of rising and falling trends can give fantasy players an advantage over their competition.

Each week we will take a look at two K% risers and two fallers, analyze what is behind those changes, and then decide if they are actionable. Given that the 2019 season is just over a week old, for this edition we will compare pitchers’ 2018 K% to their current K%. We will use RotoBaller's K-Rate Risers and Fallers premium Tool for later editions of this article.

A quick caveat related to the young season; it is sometimes difficult to draw meaningful conclusions from small sets of data, as they may not be representative of a player’s true performance overall. That being said, let’s dive into our first 2019 edition of K% Risers and Fallers!

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Risers

Matthew Boyd - Detroit Tigers

2018 K%: 22.4%, 2019 K%: 47.9%

Our first riser has been quite impressive in his first 11 ⅓ innings of work this season. Matthew Boyd has punched out 23 batters over two appearances, nearly half of the batters he’s faced! He also has a 3.18 ERA and a respectable 3.18 BB/9 rate. The 28-year-old has never been a great fantasy asset, but this start will surely catch fantasy players' attention. He is owned in just 51% of leagues, so should you rush out to claim him? Let’s find out.

A few things stand out in terms of Boyd’s increased K%. The first is his specific fastball arsenal. Last season, Boyd threw a straight fastball 34.2% of the time and a sinker 14.6% of the time. So far this season, he has almost exclusively thrown a fastball (48.1% compared to just 2.2% for the sinker). This looks like a good move on his part, as his sinker had a .352 batting average against with a mere 6.1% K rate and a 10.5% whiff rate in 2018. His fastball, on the other hand, was more successful, generating a .215 batting average against with a 21.2% K rate and a 17.9% whiff rate.

Additionally, Boyd’s 2019 fastball has been better than his 2018 fastball. His average velocity is up a bit (91 MPH compared to 90.5 MPH in 2018) and his spin rate is up as well (2,409 rotations per minute vs 2,282 in 2018). The increased velocity has its obvious benefits and the increased spin rate gives the fastball a perceived rising effect. Both of these things make the pitch harder to hit, and it shows; Boyd’s K rate on fastballs this season is 33.3% with a 40.9% whiff rate.

Boyd currently has the third-highest K rate among starting pitchers this season and his 47.9% K rate is much higher than the league-leader last season (Justin Verlander had a 34.8% K rate), so it is safe to say that his elite K rate will not last. He also does not have a dominating fastball in terms of velocity, which could hurt his K rate over the course of the season. Overall, I don’t buy Boyd’s super strikeout abilities, but he has the potential to be a back-end starter for fantasy players if he can continue to get movement on his fastball.

Lucas Giolito - Chicago White Sox

2018 K%: 16.1%, 2019 K%: 26.7%

Our second riser has been a fantasy prospect for some time but has yet to pan out. 24-year-old Lucas Giolito has had one strong and one poor start this season, resulting in a 5.73 ERA. The good thing is that he has 12 strikeouts in 11 IP. Giolito has never posted higher than a 19% K rate; has he started to finally figure things out?

There are a few interesting and positive trends across Giolito’s pitch arsenal to this point. First, his fastball is up in velocity (93.2 MPH vs 92.4 in 2018) and he is getting a higher spin rate on it (2197 rotations per minute vs 2094 in 2018). This has resulted in both a higher K rate (22.7% vs 12.4% in 2018) and whiff rate (20% vs 14.1% in 2018) on the pitch.

Giolito is also seeing more vertical and horizontal movement on his pitches across the board. In particular, his curveball is dropping about an inch-and-a-half more on average (9.76 inches vs 8.31 in 2018). The increase in movement has helped Giolito achieve a career-high whiff rate of 28.4%.

The increased strikeouts are an encouraging sign, but Giolito will need to prove that he has become a better pitcher overall before fantasy players can buy into him. His walk rate is still too high (4.09 BB/9) which limits his upside. If he can get his control in order while maintaining his strikeout rate, Giolito could certainly be fantasy relevant, but I want to see more before buying into him.

Fallers

Corey Kluber - Cleveland Indians

2018 K%: 26.4%, 2019 K%: 18.8%

This first faller has been one of fantasy’s most dominant pitchers for the past several seasons. Corey Kluber’s numbers after two starts are anything but elite on the surface; he has a 5.23 ERA with nine strikeouts over 10 ⅓ IP. Those strikeout numbers aren’t bad overall, but they are certainly not what fantasy owners expected when drafting him in the first or second round. Should these owners be concerned?

First, it is important to note that Kluber has only two starts this season and one was a dud. His first start lasted seven innings in which he gave up two runs with five strikeouts (typical Kluber fashion) but his second start lasted only 3 ⅓ innings and he gave up four earned runs with four strikeouts. That second start has a big effect on his stats now, but it won’t really factor in over the course of a full season. Even the best players have off days, so this is nothing to worry about.

Looking specifically at his strikeout rate, there really isn’t all that much to note. Kluber’s sinker and cutter have decreased a bit in average velocity (91.5 MPH vs 92 MPH in 2018 for sinker, 87 MPH vs 88.5 MPH in 2018 for cutter) but this is not something to be worried about this early in the season. His location on both pitches has missed in the middle of the plate more than last season, which may attribute to the lower K rate. Despite that, Kluber’s overall whiff rate is actually higher (29.1%) than it was in 2018 (27%).

In sum, Kluber will be just fine. There is no compelling evidence to suggest that he is in decline, so fantasy owners can breathe a sigh of relief and let him do his thing.

Chris Sale - Boston Red Sox

2018 K%: 38.4%, 2019 K%: 11.9%

Our second faller is in a similar boat to Kluber. He has been one of baseball’s best starters and strikeout pitchers of his generation, but Chris Sale has gotten off to a rough start in 2019, posting an inflated 8.00 ERA with just five strikeouts over nine IP spanning two starts. Unlike Kluber, however, there are some reasons to be concerned about Sale.  

These concerns all stem from his recent injuries. Sale landed on the disabled list (now injured list) twice last season for inflammation in his throwing shoulder and the effects were noticeable in his postseason performances. The biggest effect was diminished velocity in his fastball, and that looks to be carrying over into 2019. Sale’s average fastball velocity in 2018 was 95.4 MPH; his average in 2019 so far sits at 90.7 MPH. This is a significant drop and is definitely cause for worry.

This is particularly troublesome because the fastball has been Sale’s go-to strikeout pitch. 108 of his 229 strikeouts in 2018 came from the fastball. Yet in 2019, he hasn’t recorded a single strikeout with his fastball and has a 0% whiff rate on 50 thrown fastballs. The Red Sox were careful in easing Sale into action this preseason, so it is possible that he isn’t in top form velocity-wise. Further, many pitchers have been able to make adjustments and remain successful after losing their velocity. Regardless, these are not things fantasy owners want to hear about the top strikeout pitcher they drafted early. It’s too early to go into full panic mode, but owners should monitor Sale’s velocity closely over his next couple starts.     

All stats current as of Sunday, April 7.

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