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What’s behind Dereck Rodríguez’s poor year?

It’s not just that he was lucky last year and/or he’s unlucky this year

MLB: San Francisco Giants at Los Angeles Dodgers Gary A. Vasquez-USA TODAY Sports

Dereck Rodriguez’s success in 2018 was a fun, inspirational story. It also wasn’t going to last.

This isn’t hindsight or complex baseball analysis. It’s fairly simple stuff: If your ERA is 2.81 and your FIP is 3.74 and your xFIP is 4.56, then you’re pretty clearly pitching over your head, and your next year’s ERA is likely to be closer to that FIP or xFIP than to the ERA.

Unfortunately, Rodriguez’s ERA has soared past all the advanced metrics from last year, and his FIP and xFIP aren’t much better. The ERA is an unsightly 4.96, the FIP is 5.72, and the xFIP is 5.24. This isn’t a BABIP issue either — the quality of contact he’s given up this year has been much higher than last year, with an xwOBA of .300 (.329 on contact) in 2018 and .369 (.397 on contact) in 2019. Things are bad enough for him that the 2019 Giants, who are hurting for starters, haven’t seen fit to put him back into the rotation. So what’s going wrong for Rodriguez?

Here’s the main thing that I see: His fastball is getting walloped. Last year, by any measure, his four-seamer was a strength; now, it’s his biggest weakness. Batters are hitting .280 and slugging .559 against his fastball, while in 2018 they hit .237 and slugged .418 against it. Not only that, but he’s throwing it more often: 42% of the time this year, compared to 37% of hte time last year.

He’s not striking people out with the fastball — he’s gotten strikeouts on 9% of strikeout situations this year while using the fastball, compared to 25% last year. His velocity has dipped 0.7 MPH, from 91.6 to 90.9 MPH, he’s walking more guys with the fastball than he did last year, and his exit velocity has gone up by almost 2 MPH.

In short, a pitch that was Dereck Rodriguez’s bread and butter in 2018 has become his moldy bread and gross oily margarine spread in 2019. So why did that happen?

Obviously, when it comes to fastballs, the first thing you look at is velocity. And, like I mentioned before, his four-seam velocity is down by 0.7 MPH this year, when compared to last year. That’s not the whole story — 0.7 MPH isn’t that much — but it certainly is part of it. Is that velocity drop, on its own, going to raise opposing wOBA from .311 to .410? That seems unlikely.

The problem seems likely to be approach and deception. Batters are swinging more at balls in the strike zone and less at balls out of it. Since Rodriguez is in hitter’s counts all the time, hitters can sit on his fastball and then destroy it. Since it’s harder for him to get hitters to swing at balls out of the zone, his walk rate has increased and his strikeout rate has declined — his K% is in the bottom 4% of the league, according to Statcast — which means that there are guys all over the bases when he gives up big hits.

And the big hits are plentiful this year. Rodriguez is also giving up more fly balls and more balls in the air. When you combine that with batters hitting the ball harder and the ball itself being juiced, those changes in contact have been a big part of Rodriguez’s inflated 18.5% HR/FB rate. Lots of baserunners and lots of home runs is a recipe for unpleasantness, and that’s what we’ve seen this year.

The decline in Rodriguez’s fastball also affects his off-speed stuff. If you’re a little less afraid to sit fastball, then you can wait for a breaking pitch and put a good swing on it. His changeup especially has lost effectiveness this year; it’s still coming in at the same velocity it was last year, but with the decline in the fastball, it’s become a little more hittable and less of a weapon to put hitters away.

It’s not like Rodriguez isn’t trying to fix things. His vertical release point is noticeably lower than it was at any point last year, while he adjusted his horizontal release point a couple of months ago. And it seems to be working, too. I touched on Rodriguez’s struggles a month and a half ago when making a larger point about how all of the starters have been bad, and his numbers have improved since then: more guys chasing bad pitches, more whiffs, more good times.

But that hides a simple fact: Dereck Rodriguez is a reliever now. Relievers get more swing throughs, so the marginal improvements it seems like he’s made are really just a function of a different role. And the Giants don’t need relievers; they need starters, and they need them now.

Last year, it looked like Rodriguez could be a long term solution in the rotation; maybe not the star his ERA would indicate, but at least a major league-quality guy to run out there every fifth day. This year, it looks like it’ll be a struggle for him to stay in the majors at all. One of the team’s more encouraging stories from 2018 is putting out a miserable sequel in 2019, and there aren’t any answers in sight.