Better Luck This Year: Evaluating Early Season Differences in Pitcher Strikeout Rates

Early in the baseball season we are always trying to judge what is real for a player or what could simply be a sample size issue. It’s one of the biggest issues in evaluating decisions for DFS. How much should we trust what Player A has done this year compared to what he’s done over his career? It’s tough. For this piece we’ll focus on pitchers who’ve shown dramatic differences in their K/9 stats from last season (both increases and decreases).

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Let's start with three of the guys striking out a lot more batters this season.

[table id=218 /]

Chris Sale 

He’s the early season runaway favorite for the American League Cy Young and that even takes into account his “disastrous” fifth inning Sunday against the Twins. Sale’s been an absolute beast this season, K-ing guys at Kershaw levels (12.72/ 9) and walking less than two batters per nine. When a guy switches teams and immediately yields super solid results there’s a good chance someone on the staff got to him and implored a change in approach.

That appears the case with Sale who last season threw his two-seam fastball 56% of the time and his four seamer a whopping 0%. This year? He's throwing the latter 30% of the time and the former 19%. This is to say, he’s mixing up his fastball offerings while also going a bit more to the change up and slider. That’s led to an uptick in swings outside of the zone and also greatly reduced his in the zone contact. Batters are flummoxed. Add on that Sale’s average fastball velocity is at it’s highest since 2010 and you have a guy who  should be able to sustain these kind of returns.He’s the early season runaway favorite for the American League Cy Young and that even takes into account his “disastrous” fifth inning against the Twins on Sunday. Sale’s been an absolute beast this season, K-ing guys at Kershaw levels (12.72/ 9) and walking less than two batters per nine. When a guy switches teams and immediately yields super solid results there’s a good chance someone on the staff got to him and implored a change in approach.

Verdict: Sale’s numbers this season appear the real deal.

Edinson Volquez

Another starting pitcher with a uniform change. Volquez goes from the Royals to the Marlins and all of a sudden started striking guys out at a clip he hasn’t enjoyed since he was in Triple A a decade ago. He’s decided to actually throw his fastball now, chucking it 25% of the time up from 11% and 12% over last two years. He also scaled down his use of the knuckle-curve from 25% to 16%.

But just because he’s striking more guys out doesn’t mean it’s all lollipops and rainbows. Dude’s also walking basically everyone he doesn’t K (6.91 BB/9) and carrying around a 4.58 xFIP. Batters aren’t chasing balls out of the zone with him so while they are swinging and missing more in the zone, if he doesn’t get that it’s a walk.

Verdict: While there’s been a change in Volquez’s approach leading to more K’s, it also seems to be having an adverse effect on everything else. I’m staying away here because this kind of profile has blow up written all over it.

Jacob deGrom

Jacob deGrom, like Sale, has seen his strikeout stuff go from pretty damn good to “WTF, holy Sh@#” territory in a relatively short period of time. Like one season. He’s striking out almost 13 batters per nine up from about a batter an inning last season. With it has come a spike in walk rate limiting his ability to go longer in games. So what’s changed about deGrom? First off he’s throwing the ball harder, a lot harder. His FB is up 2 MPH from last year and averaging 95 MPH. In fact, all of his pitches (fastball, slider, curve and change) are all up about 2 MPH across the board. What that’s done is limit batter’s ability to make contact in the zone. Last year hitters made in the zone contact about 85% of the time. This year it’s down to 74%. That strikes me as a guy blowing hitters away.

The walks are coming from hitters not chasing outside of the zone as much but I can imagine this number regressing as the season goes on. That’s somewhat of a guess and he’s run a little bad in facing some more patient teams early in the season.

Verdict: I think the K's normalize and the BB's drop. He likely regresses back to his career numbers but we do need to keep an eye on that velocity.

And here are the guys with the biggest drop offs.

[table id=219 /]

Stephen Strasburg
The big move for Strasburg was abandoning the wind up all together and pitching solely out of the the stretch. I’m not sure this is the primary reason for his dip in strikeout stuff, but through 6 games he’s K-ing less than eight batters per nine with a 3.51 xFIP (.70 higher than his career numbers).

After throwing his slider 17% of the time last season, he’s now throwing it just a hair under 8% and instead going more to the curveball (18%, up from 12%) and changeup (18% up from 13%). Where Stras is really struggling is the contact within the zone. Even though his velocity is up this season, hitters are making contact about 90% of the time in the zone. Where the fastball used to be his weapon in the zone, that isn’t the case this season. His Pitchf/x Value on the fastball has dropped from 1.01 to 0.58. It means he simply isn’t getting it past batters and the K’s are suffering.

Verdict: I’d be worried about Strasburg here. With the dramatic shift in approach on the mound has possibly come a sustained drop in strikeouts.

Danny Duffy

The issue here is which Danny Duffy is the real one? Is it last year’s 9.42 K/9 numbers or 2015’s 6.72 K/9. If you believe the latter is the actual dude, then there’s nothing to worry about in the sense that he’s just an average pitcher and we can move on. But if you believe the 2016 campaign was the Duffy we should expect then you’ve been crushed by his performance this season. Because he’s been pretty damn bad. He’s striking out less than six batters per nine and carrying around a 4.66 xFIP. He’s been lucky with the 3.50 ERA mostly because he’s likely run hot on keeping balls in the park.

Duffy’s pitching a lot more like a “junk” guy this year, cycling down his FB% from 60% to 48% and greatly increasing his slider and changeup. It isn’t working. He’s lost 2 MPH on the heater and batters aren’t chasing him out of the zone anymore. That could be a death knell for a dude who is pitching primarily off speed stuff.

Verdict: It’s looking more like Duffy’s 2016 season was a total outlier.

Yu Darvish

Oh Yu, I long to roster you. I just can’t quit this guy and yet he keeps popping into my lineups. Darvish has spent a post-Japan career in the majors as a total ace, K-ing a ton of dudes and basically being who we thought he’d be. But then this season the K’s have dropped about 20% and we are left wondering.

Dervish is making major changes to his profile just to start the season. He’s throwing the fastball way less (from 59% down to 50% this year) and using the slider and cutter each about 50% more than last year. That’s a rather dramatic shift in approach for a guy who could command four pitches over the course of his career.  And he’s encountering issues all over the place. For starters. batters aren’t chasing as much (O-Swing% down 4%) but when they do they’re actually making contact (O-Contact% 63% - up from 59%). Hitters are also making way more contact in the zone this season (88% up from 81%) which means he just can’t make mistakes in the strike zone. All of this combined with a decreased in Swing % and I’m worried about the guy.

Verdict: Yu’s been a dynamo in years passed, but teams might be figuring out his schtick. If you can avoid chasing him out of the zone then the walks pile up.

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