What's behind Julio Rodríguez's down year (at least by his standards)? Three problems for Mariners slugger

While mining social media posts for article ideas should be scorned at nearly every turn, for oftentimes it's the mark of a wayward creative soul, we must admit we felt inspired by a tweet on Tuesday night from veteran ballwriter Rob Neyer. "The Mariners are the Royals without Bobby Witt," he tweeted to minimal response. 

Our inspiration had less to do with the base-level reading of Neyer's words (that Witt is the transformative force lifting the Royals above and beyond) and more about the subtext: specifically, what it says of the player who was supposed to be the Mariners' Witt: Julio Rodríguez, the 23-year-old who willed himself into a starting center fielder. Lest anyone forget, Rodríguez entered this season with more than twice Witt's career Wins Above Replacement total -- and that despite appearing in 21 fewer games. Yet this season has been a letdown, to the extent that he's going to finish with career-low marks in every notable statistic: home runs (16), steals (22), each of the triple slash line measures, OPS+ (110), WAR (3.6), and so on. (Mind you, most MLB teams would gladly take a 110 OPS+ and a nearly four-win showing from their center fielder.)

Rodríguez and the Mariners, in turn, are more likely at this stage to miss the playoffs than make them. (They enter Wednesday three games back of the closest wild-card spot.) Witt and the Royals, conversely, are in firm possession of the second wild-card position. It's fair to wonder where the Mariners would be right now if Rodríguez were applying the finishing touches to a season that resembled his more typical output.

Instead, Rodríguez and the rest of Seattle have to wonder: where did things go wrong this year? Below, we've identified three factors that explain his relative step back.

1. Altered swing, approach over offseason

A funny thing about Rodríguez's season is that the Mariners were convinced he was in for his best season yet back in the spring. 

The optimism flowed from the changes Rodríguez made to his swing and his approach during the winter. Then-manager Scott Servais, replaced earlier this summer by former catcher Dan Wilson, told Adam Jude of the Seattle Times that a six-pitch walk Rodríguez worked early in the season was a "sign of a young superstar maturing." 

Rodríguez himself said he felt he was on the cusp of a big year after streamlining his operation.

Six-plus months later, it's fair to say those changes haven't had the desired effect -- it's possible, even, that they negatively impacted his season. We'll touch more on the swing elements and how they manifested in later subheadings. So far as this one goes, we'll just note that whatever approach shifts he attempted to make haven't taken.

Indeed, Rodríguez is walking the exact same amount he did last season; he's chasing more often than he did in 2022 (albeit less often in 2023); and so on. Here's a look at some of his most important plate discipline statistics, including his SEAGER score -- a fancy pants statistic created by Robert Orr that attempts to provide a single measure for a batter's approach. (Do note that the higher the SEAGER, the better.)

We'll concede that a batter's approach is a difficult thing to capture statistically, and that Rodríguez could have leveled-up in ways that don't show up on a statsheet. But, from this perspective, it appears the hype about a more mature approach was hot air.

Speaking of complex systems, what about those swing changes?

2. Worse against velocity

"You're going to start noticing some differences throughout," Rodríguez told reporters about his modified swing during spring training. "But I feel like those were some of the things that I tried cleaning up. Just to make sure that I don't have as much movement. I'm a big guy, I don't need to do a lot to be able to drive the ball."

In theory, there's nothing wrong with a batter wanting to become more efficient. Any extraneous movement could leave a hitter out of position, costing them time they can ill afford to waste. That can result in more foul balls, a worse point of contact, or even more swinging strikes; said batter may also make worse swing decisions, since they feel compelled to make earlier calls on whether or not to offer at a pitch.

You can understand, then, why Rodríguez and whoever instructed him on such matters might want him to tighten up his swing a bit.

Unfortunately, the "after" version of Rodríguez looks a lot worse than the "before" version in a few different ways, including his performance against velocity. Take a look at how his production has slipped against pitches clocking in at 92 mph or above:

For those wondering, the league-average mark this season on pitches thrown 92 mph or harder is a .740 OPS. Rodríguez is still above that threshold, albeit not by as wide of a margin as one would like given his youth (he's not at the age where you would expect his bat speed or rotational acceleration to be in deep decline) and talent level.

If we're being fair to Rodríguez and his hitting coaches, his decay against velocity didn't begin this season and can't be blamed wholly on his swing alterations. He experienced a drop-off last season that was eschewed by better overall marks. That decline -- which may have been the impetus for the reworked swing and approach -- has been exacerbated by further deterioration this year.

There's one other decline we feel helps explain Rodríguez's declined performance. 

3. Not pulling ball as often

We referenced "point of contact" earlier. It's a simple measure: where, exactly, does the bat connect in relation to the plate. It's a piece of quantifiable information that's not yet publicly available, but that likely drives some decisions (and explains some performance swings) within front offices across the majors.

Although we don't have that data, we can use proxy measures to figure out when a player's point of contact has changed -- be it for the better or not. Rodríguez, to our eyes, appears to be a case where his point of contact has declined.

To wit, Rodríguez entered Wednesday sporting a .124 ISO (that's slugging percentage minus batting average), a mark that puts him in company with Steven Kwan, Anthony Volpe, and other batters whose power output should not be associated with someone like Rodríguez. For reference, he came into this season with a career .216 ISO.

What's caused Rodríguez's power outage? You might point to how his average exit velocity is down year to year, and he's recorded a lower frequency of batted balls with a 95 mph or higher exit velocity. We think that's a byproduct of the bigger culprit: his point of contact. The surest way to slug, or to make hard contact, is to pull the ball (especially in the air, since those are where you get extra-base hits). 

Rodríguez's batted-ball spray breakdown (courtesy of TruMedia) reveals that he's pulling the ball less frequently than at any prior point in his big-league career. Observe:

That's a stunning year-to-year decline in pull rate. We're not going to get too deep into the philosophical weeds. We're aware that there are different schools of thought about how much batters should prioritize pulling the ball. But our rule of thumb is that you generally should not mess with what works unless there's a good reason for it. Given that Rodríguez had enjoyed a great deal of success pulling around a third of his batted balls entering this season, we tend to doubt that he or the Mariners intended for his tweaks to have this kind of impact on his game.

We're not swing doctors, so we're not going to pretend we have the magical fix for Rodríguez going forward. Our takeaway is that Rodríguez's season -- which, again, still places him among the top 10 or so center fielders in the sport -- is a bit of a warning for how well-intended maintenance can have unforeseen consequences.

Our hope is that Rodríguez can retool his swing this offseason, setting the stage for him to remind people why he appeared on or above Witt's level just six months ago.