Short of the Twins acquiring another starter, Randy Dobnak and Lewis Thorpe will be battling alongside Devin Smeltzer for the final two slots in the rotation. How long those spots will be held remains to be seen, but today we will take a dive into the numbers of Dobnak and Thorpe and predict who will have the bigger impact in 2020.
The two young hurlers provide an interesting juxtaposition. Thorpe is an international signing from Australia that has graced Twins prospects lists as he’s worked his way through the system. Dobnak on the other hand was an undrafted Uber driver who seemed to come out of nowhere.
Thorpe is a swing and miss FIP-god who is easy to dream on, while Dobnak’s rather stunning 1.59 MLB ERA screams for regression. They don’t even throw with the same arm (Thorpe is a southpaw). However, both will be looking to make their way into Minnesota’s rotation due to Michael Pineda’s suspension and Rich Hill’s experimental arm surgery. Let’s take a look at who we should expect more from this year.
We’ll start by looking at some traditional stats and then dive into MLB Statcast numbers.
Before we get too far, it must be said that both pitchers' MLB numbers are based on a small sample size, but they’re all we’ve got, and they do trend pretty well with how both pitchers performed in the minors in 2019.
Although Dobnak’s FIP doesn’t quite match his sterling ERA, it’s still excellent at 2.90. While Dobnak doesn’t get a ton of strikeouts (RDLARK has a great blogpost explaining how that may change), he also doesn’t walk anyone and gets a ton of ground balls (52.9%).
Since joining the Twins organization in 2017 his numbers have been consistently solid across all levels and he may be one of those guys who out- performs his FIP. It’s also worth noting that ZiPs projects Dobnak to be the team’s fourth-best starter based on ERA and FIP, trailing just Rich Hill, Jose Berrios, and Jake Odorizzi, and ahead of Michael Pineda and Homer Bailey.
Thorpe was basically the anti-Dobnak in 2019. Thorpe gets a ton of strikeouts but he was also hurt by giving out a lot of free passes. Absurdly, Dobnak gave up only one home run between AAA and MLB (though he did give up six in AA), while Thorpe surrendered 16 dingers in less innings. Thorpe’s FIP greatly outperformed his ERA at both levels and he allowed a .438 BABIP with the Twins, so there is reason to believe his numbers will improve.
Let’s dig a little deeper and get into the pitch mixes:
Both Thorpe and Dobnak throw a four-seam fastball with less than stellar spin rates (Thorpe’s is in just the seventh percentile). Dobnak’s heater beats Thorpe’s by a few ticks, but neither pitcher is going to blow anyone away. Dobnak’s results were really good, although his xwOBA suggests some regression, while Thorpe’s heater didn’t fare well, but he did get more swings and misses.
The main difference is that Dobnak doesn’t need to rely on his four seamer as much as Thorpe because he throws his highly-effective sinker more frequently, leading to his high ground ball rate.
With an underwhelming four seamer, Thorpe is going to need to rely on his secondary pitches if he hopes to succeed as a starter. Thorpe features three secondary pitches (slider, curve, and changeup), but his slider was his only above average pitch. Fortunately, Thorpe’s slider is really good and it gives him a solid floor as a lefty reliever.
But to succeed as a starter, Thorpe must find a way to get better results from his other secondary pitches. In an admittedly small sample size, both his curve and changeup (which he mixes in against righties) were crushed. His xwOBA on the curve suggests it might not have been quite so bad and he did get a fair number of whiffs on his changeup, but there’s no denying the numbers were ugly.
Dobnak’s secondary pitches fared much better than Thorpe’s. His slider is unlike Thorpe’s, as it is more 12 to 6 than sweeping (Statcast identifies it as a curve), but like his teammate, he gets great results (Dobnak’s whiff % is even higher than Thorpe’s).
Dobnak’s other secondary pitch is his changeup, which he mostly mixes in against left-handed hitting. Again, it’s a small sample size, but hitters did next to nothing against it. Dobnak also had the 10th-lowest barrels/plate appearance rate of all MLB pitchers at just 1.7% (all pitches).
It’s obviously too early to give up on Thorpe and also too early to declare Dobnak a success, but Dobnak has given us more reason to believe thus far. Although Dobnak doesn’t have the prospect pedigree of Thorpe, he’s succeeded at every level and looked anything but overwhelmed in his first big league stint.
If things go as planned, both could eventually be pushed out of the rotation by Pineda and Hill, but they should get every chance to show what they can do in 2020. Finding a way to mix two more quality starters into the rotation is a problem Minnesota would count itself fortunate to have.
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