Strikeout Rate Risers and Fallers for Week 7: Buy or Sell?

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

Aaron Nola, Philadelphia Phillies

2017 K-Rate: 26.6%; 2018 K-Rate: 23.9%; Last 30 Days: 25.2%

Although he went largely unnoticed on a bad team, Aaron Nola quietly emerged as a top-tier pitcher for the Phillies in 2017 and became a top-15 fantasy pitcher coming into this year. His first four starts of 2018 went similarly to his breakout 2017, as he boasted a nice and shiny 2.22 ERA in 24 1/3 innings. But two components were missing: the whiffs and the control. His strikeout rate sat at just 16.1% and his walk rate was 9.7%. Given his track record, it stood to reason that both of those numbers would improve. But had we been too premature in declaring Nola as an ace?

If the previous two weeks are any indication, that answer is no. Nola has dominated over his last five outings, going 4-0 and striking out 36 against four walks. That comes out to a 27.9 K% and 3.1 BB%. Aside from the obvious improvement in control, what changed? A slight uptick in fastball velocity — from an average of 92.0 mph in his first four starts to 92.6 mph over his last five — certainly helped. The changeup, however, is the pitch really turning things around for the right-hander. Not only is he using it more as the season goes along, but he's also missing more bats with it.

Take a look at his whiff rate on the pitch as the season has gone along:

That's a change in whiff rate from 9.1% over his first four outings to 27.3% in the last five. When the pitch isn't getting swings and misses, it's generating a ton of groundballs — three-fourths of the time, to be exact.

If Nola can get more consistency out of his curveball, traditionally his best swing-and-miss offering, his rise to ace status seems all but certain when paired with his command. After getting a 19.9% whiff rate on the pitch in his first three major-league seasons, that number is down to 15.1% in 2018. The breaking ball is starting to come around, though; over his last two starts, his swing-and-miss percentage on the curve sits at 18.3%.

Overall his swinging-strike rate has risen to a career-high 11.7%. This strikeout surge is legitimate, and his value continues to ascend. If you're trying to acquire a top starting pitcher but don't want to pay the price for someone like Max Scherzer, Nola may be the man to target.

German Marquez, Colorado Rockies

2017 K-Rate: 21.0%; 2018 K-Rate: 20.9%; Last 30 Days: 24.1%

Coors Field makes any Rockies starting pitcher hard to trust. Not only does the thin Denver air cause more baseballs to leave the yard, but it also leads to less movement on pitches and, thus, fewer strikeouts. German Marquez tried to buck that trend last year. Although he wasn't able to escape the long ball (15 HR in 80 1/3 innings), his strikeout rate at home (22.5%) was above average and his ERA (4.59) was, while not great, still manageable. If he could just improve on the road and stay average at home, there was optimism about what Marquez could do in his second full season. The first part of that equation has held up (1.96 road ERA), but he's been dreadful at home in 2018. He has a 10.34 ERA in four home starts and has yet to make it through the fifth inning in any of those outings. Does his rising strikeout rate provide any hope?

Yes and no. His road K% is a promising 25.3%. Good news there. Marquez's punchout rate at home, however, has plummeted to 16.1%. A large part of his problem is a decline in his curveball's effectiveness. Its pitch value currently sits at minus-2.7 after coming in at 3.3 — his highest mark on any offering — in 2017. His whiff rate on the pitch is down to 13.1% from 15.3% in 2017. Hitters are recognizing it better, only swinging at it 39.8% of the time after going after it 43.0% of the time in 2017. They're also chasing it out of the strike zone 30.9% of the time as opposed to 36.7% last season. The curveball is getting more vertical drop overall than in 2017, but that movement decreases significantly at Coors, as illustrated in this chart:

The elevation is killing Marquez's curveball movement and playing a large role in his lack of effectiveness at home. Some of his other pitches are to blame as wlel. Despite more swings and misses on his four-seamer and slider, he's also seen a drop-off for his sinker and changeup whiff rates.

On a positive note, his strand rate (67.3%) and batting average on balls in play (.356) should regress to the mean and send his numbers in a better direction, though the latter may stay higher than league average due to his home ballpark. He has also reduced his hard-contact rate from last year's 34.5% to 30.3%. Despite these positive signs, though, Marquez's unreliability makes him nothing more than a streaming option when he's starting on the road. He has an electric right arm, but like most pitchers, he simply can't be trusted at Coors Field right now.

Fallers

Corey Kluber, Cleveland Indians

2017 K-Rate: 34.1%; 2018 K-Rate: 24.8%; Last 30 Days: 20.6%

Since 2014, only Max Scherzer and Chris Sale have more strikeouts than Corey Kluber. His strikeout rate is sixth among all starters. That's why it's a surprise to see him on the K-rate faller list at all. Yet, in addition to giving up a bunch of home runs, Kluber has been merely average when it comes to strikeouts over his last 30 days. His overall strikeout rate also pales in comparison to last year's dominance. Results-wise, he's been the same pitcher as always: 2.34 ERA (13th in baseball) and 0.84 WHIP (4th). But his K% ranks 31st among qualified pitchers, and that number drops to 52nd over the last 30 days.

When looking at Kluber's FanGraphs profile, the first detail you may notice is his age: 32. As is the fear for pitchers his age, his velocity has slipped a bit this year — the sinker, cutter, and four-seamer have both fallen by almost 1 mph. But that's hardly enough to get worked up over since he's not a power pitcher. Movement is what matters for Kluber when it comes to his strikeouts, particularly on his nasty cutter, slider, and changeup. Encouragingly, the movement on all of his pitches is as good as or better than they were in 2017.

However, his overall SwStr% (10.5%) still sits below league average and his O-Swing% down by four percentage points. The reason is he's getting fewer whiffs on each of those three putaway pitches so far this season, with especially sharp drops for the slider and cutter.

Kluber has primarily been getting into trouble early in counts, as hitters are being more aggressive against him on the first pitch. He's already allowed 10 home runs in 65 1/3 innings, with four of them coming in the first inning. A slight change in pitch mix may be leading to his problems, as he's throwing more fastballs on the first pitch and fewer sliders. Given that he throws a lot of strikes, hitters may be more inclined to swing early in the count against him before they get behind and he drops a wicked slider or changeup on them.

If you remember, Kluber wasn't his normal self to begin 2017 either. He still went on to win the American League Cy Young award. His slider had a similar whiff rate through May 2 of last season as it does this year.

That's not to suggest Kluber is a sure bet to rebound to his eye-popping 34.1 K% from last year, especially with the whiff rate on his other pitches down, too. But it does show he's an elite pitcher who can make adjustments as the year goes on. Kluber is still one of the best pitchers in the game, and a larger sample size is needed before it can be definitively determined his ability to miss bats is diminishing. In the meantime, he's still finding ways to get hitters out. If you're considering selling due to the strikeout drop, your asking price should still be very high.

Cole Hamels, Texas Rangers

2017 K-Rate: 17.1%; 2018 K-Rate: 25.1%; Last 30 Days: 21.8%

Last year, age seemingly caught up with Cole Hamels. He had his worst season as a major-leaguer, posting a 4.20 ERA in 148 innings and missing nearly two months with an oblique strain. Most alarmingly, his strikeout rate fell off a cliff, dropping to 17.1% after sitting between 23-24% for the majority of his career. So it was a bit surprising to see the southpaw rack up 30 strikeouts through his first 22 innings in 2018. With a new slider and a renewed focus on throwing his cutter, Hamels seemed to be making changes that would result in more success.

Through three outings, his changeup continued to be his primary putaway pitch with a whiff rate sitting at 32.3%. Suddenly, his cutter was nearly as effective, registering a 21.3% whiff rate. Considering the pitch had never registered more than 10.9% swing-and-miss rate, however, it seemed unlikely to hold up, and that has been the case. Since April 13, the cutter has fallen back to earth with a below-average whiff rate of 7.9%, playing a big role in his overall decrease in strikeout rate. The pitch is still effective, though, thanks to its 53.4% groundball rate

However, there's still reason to believe Hamels can be at least an average strikeout pitcher and last season was simply a down year. The southpaw's overall whiff rate is nearly identical to his 2016 mark (13.0%), up significantly from 2017 (10.0%). In addition to developing a second breaking pitch, his curveball has returned to prior form after being a poor offering for him in 2017. It's been inconsistent from game to game — a big reason it's important to have a slider paired with hit — but the bender is missing bats the same way it did in 2016, too (15.5%). While Hamels isn't an All-Star-caliber pitcher anymore, he's still proving to be a useful back-end fantasy starter.