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Eduardo Rodriguez’s strong start has been fueled by more changeups and fewer walks

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Eduardo Rodriguez is doing a few things differently this year and it could mean big things for a pitcher already at the top of the Red Sox’s rotation.

Seattle Mariners v Boston Red Sox Photo by Kathryn Riley/Getty Images

On Sunday, Eduardo Rodriguez pitched what many people would call a gem. He worked seven innings of three-run ball while striking out eight batters, helping the Red Sox to a 5-3 win over the Mariners. It was just what any staff would want from a pitcher who was originally pegged to be the Opening Day starter.

Sunday’s outing was far from an anomaly compared with Rodriguez’s other starts from this season, even if it did mark his first seven-inning effort since his final appearance of 2019. Tossing aside that tidbit, Rodriguez has been fairly consistent and effective to start the 2021 campaign. Through four starts (23 total innings), he is sporting a 3.52 ERA, which is solid enough but is underselling what his marks in xFIP (2.82) and xERA (2.48) illustrate. Although Nathan Eovaldi has been good for most of the season as well, there’s no denying that Rodriguez is once again the best (healthy) pitcher in the rotation. It’s a title he first claimed at the end of his masterful 2019 season when he posted a 79 ERA- and, for my traditional readers, flirted with 20 wins.

Rodriguez isn’t just rinsing and repeating what he did in 2019 this year, however. He has made some pretty noticeable changes to his approach, namely increasing his changeup usage (especially relative to his other offerings) while drastically cutting his walk rate. Both of these adjustments are at least partially responsible for some of the promising results we’ve already discussed.

Let’s start with what he’s doing in terms of his pitch selection. Throughout the last few seasons, Rodriguez has done a solid job of mixing his pitches, going from relying heavily on his fastball to spreading the love a bit more. His fastball remained his most used pitch, but instead of throwing it more than 60 percent of the time, he was offering it up in the 30-40 percent range. That was until this season.

Plenty of pitchers rely on a non-fastball pitch as their primary offering, but it is still a striking thing to see, especially in an era of heightened velocity. Add in the fact that Rodriguez has historically been a heater-reliant pitcher and it makes what he’s been doing this year even more interesting.

Through his first four starts of 2021, Rodriguez’s favored pitch has been his changeup. Of the 343 total pitches he’s thrown, 31.2 percent have been changeups, according to Baseball Savant. For historical context, Rodriguez has thrown his changeup 20.4 percent of the time across his entire career, even if it has been creeping up in usage for the last few seasons. Now, throwing one pitch nearly a third of the time isn’t evidence that a pitcher is relying on it way more than others by itself, but Rodriguez has thrown all of his other pitches at rates below 30 percent (including a pretty nasty slider).

It makes a lot of sense for Rodriguez to move away from being a fastball-first pitcher. His fastball is passable but far from exceptional. Rodriguez is in just the 19th percentile of MLB pitchers in fastball velocity this season and the 24th percentile in fastball spin rate, according to Baseball Savant.

The rationale becomes even stronger when we really look at Rodriguez’s changeup, which has always been an interesting pitch. It isn’t all that much slower than his fastball and stands out more for its horizontal break than its vertical drop. According to Baseball Savant, Rodriguez is averaging 18.2 inches of horizontal movement with his changeup this season, which is in the same ballpark as his historical performance for the most part. Baseball Savant also shows that such an amount of break is 3.6 percent greater than the average for other similar changeups, tying him for 14th among qualified MLB pitchers. Even if that evidence doesn’t make Rodriguez’s changeup one of the one or two best in baseball, it certainly shows that its an above average pitch, especially in comparison to the rest of his repertoire. In addition, according to pitch values on FanGraphs, Rodriguez’s changeup is tied with Jacob deGrom’s changeup and Hyun-Jin Ryu’s changeup as the 12th-most valuable such offering this season.

The value of Rodriguez’s changeup isn’t just a product of its movement but also of where its being located. As the chart below illustrates, Rodriguez is consistently keeping his changeup low, rarely ever missing up with it.

Per FanGraphs

Speaking of locating well, let’s get to the second half of the equation. Although he has not been Corbin Burnes, Rodriguez has walked a total of two batters in 23 innings this season, making for a walk rate of 2.2 percent. According to Baseball Savant, he is in the 97th percentile of MLB pitchers in the statistic, helping him produce a xwOBA that ranks in the 86th percentile of MLB pitchers. It’s quite the reversal for Rodriguez, who may not have had a terrible base on balls problem but who also had the 11th-highest walk rate among qualified pitchers in 2019 (8.7 percent). To avoid free passes, Rodriguez has simply made throwing strikes a priority, as he has run the count to 3-0 only twice, to 3-1 only once and to full 12 times this season. He’s also been more aggressive early against batters, as he has thrown a strike on the first pitch of a plate appearance 66.3 percent of the time, which would be a personal best if it held for the rest of the season.

Therein lies the rub. We can expect Rodriguez to be a very good pitcher for the rest of 2021. He’s done it in the past and based on what we’ve seen so far this season, its more likely that he will get better instead of getting worse. However, it remains to be seen if Rodriguez can keep walking batters so infrequently and if he will maintain his reliance on his changeup. Those two factors have stood out the most through his first four starts and could be what fuels another step forward for the Red Sox’s current No. 1 starter.