Can Twins Rookies Avoid the Regression Bug?

Twins fans have seen it time and time again: a player splashes onto the scene with a phenomenal rookie year and then quickly experiences the full weight of regression in the following season. Baseball is a game of ebbs, flows, and adjustments, which can often hit hardest after an introductory burst of success.

Most recently we saw this convention play out with José Miranda, whose brilliant rookie campaign in 2022 gave way a to complete disaster this year, seeing him turn from key contributor to non-factor and planning uncertainty. The same could be said for Nick Gordon, though he technically was not a rookie last year. Miranda went from a 116 OPS+ in 2022 to 56 in limited time 2023; Gordon dropped from 111 to 35.

Looking back through Twins history, there are plenty of other examples that might quickly come to mind, such as Danny Santana (130 OPS+ in 2015, 46 in 2016) and Danny Valencia (119 in 2010 to 86 in 2011). Both times, the Twins as a team took a massive step backward from year to year, in some part because they were counting on those young standouts to grow or at least hold steady rather than fall off.

Which brings us to the outlook for the 2024 team. The Twins received a historic level of contribution from their rookie class this past season, with Edouard Julien, Royce Lewis and Matt Wallner becoming the first trio to post an OPS+ of 120 or higher since Lou Gehrig and the 1925 Yankees. In fact, they were all above 130, meaning each of these three MLB newcomers was at least 30% better than the average hitter.

It's a remarkable accomplishment that sets an almost impossibly high bar for next year; there's almost zero chance all three finish the 2024 season at that threshold, even if they all have good seasons.

The big question, as the Twins now plan around this emergent new youth core, is how much of a drop-off we can expect. Ideally, any marginal decline in rate performance will be counteracted by higher volume (fullish seasons from each, as opposed to the 900 plate appearances they collectively made in 2023) plus improvements from other key players – namely Carlos Correa and Byron Buxton.

Here's a rundown on each of the Twins reigning standout rookies and what to look out for in 2024 in terms of regression risks, and how they can overcome them.

Edouard Julien
Julien slashed .263/.381/.459 with 16 homers, 16 doubles and three steals during his rookie campaign, which featured a brief debut in April and a permanent call-up in May. There are certain aspects of his game that make him feel somewhat regression-proof; namely, a level of plate discipline that is literally unrivaled throughout the league.

Julien swung at only 14.8% pitches outside of the strike zone, according to Statcast, which was the lowest rate in the baseball among players with 400+ PA, beating out runner-up Juan Soto (17.2%). That's not a fluke, that's just who Julien is, and it's a big reason why concerns of a complete offensive fall-off are minimal. 

What does regression look like?
While his discerning patience is a core skill that provides Julien with a solid offensive floor, it's no lock that he'll be able to approach his ceiling the way he did as a rookie. What made him so exceptional in 2023 was that in addition to all the walks, which helped produce a .381 on-base percentage, he also did major damage on pitches in the zone. 

Some of that production was inflated, no doubt. Julien struck out a lot, and posted a .371 batting average on balls in play (BABIP), so if all things stay the same profile-wise, we should probably expect his .263 average to drop significantly next year. His expected batting average (xBA) was .233, per Statcast. Meanwhile his xSLG was .427, so we'll see if he can keep the power production pumping. 

If Julien slashes something like .240/.350/.420 next year, while it'd be a significant step backward, he would still be a solid contributor. I'm inclined to believe the 24-year-old can maintain as a top-tier offensive player simply because he's done it literally everywhere, without exception, but the indicators of coming regression are not hard to see. 

Royce Lewis
Lewis shocked the baseball world in 2023 by returning from his second straight ACL surgery and playing at a legitimate MVP-caliber level for 70 games, then kicking that up a notch in the playoffs. He is almost by definition bound for regression because the standard he set is so extraordinary, but the third baseman has given us every reason to believe he can sustain as a star-caliber player.

After slashing .300/.317/.550 in a 12-game MLB debut in 2022, Lewis came back in 2023 to put up a .309/.372/.548 line in 70 games in 2023, plus a 1.119 OPS with four homers in the playoffs. He's set up as the centerpiece of the 2024 lineup. Which could be precarious.

What does regression look like?
It seems likely that Lewis is going to end up being a really good MLB player, maybe a multi-time All Star and maybe even one day an MVP. But people should not assume it will be an immediate and smooth journey even if he's started it with a bang. Turning 25 next season, Lewis still only has 280 major-league plate appearances – less than half of a full season's worth – and within that he's been an aggressive hitter whose pursuit of power has paid off.

That payoff doesn't always remain steady. MLB pitchers are very smart and adaptive. Lewis could be in for some performance-based regression beyond what the underlying metrics already suggest. He had a .354 BABIP in 2023 and his exceptional wOBA (.393) was far higher than his xWOBA (.349). The former ranked 13th among big-leaguers (200+ PA); the latter ranked 65th.

Lewis is still a developing player whose skill set and approach don't feel quite crystallized. Certainly the rapid and recent ascent of his power tool bodes well, as do the glimmers of discipline he's shown. But he's still got some things to prove in terms of plate approach and consistency.

A full-on regression might look something like he put up in his last full minor-league season, between Single-A and Double-A in 2019, when he slashed .236/.290/.371 in 566 plate appearances. That's obviously on the extreme end. But everyone should be realistically bracing for some level of drop-off from what we saw in the last 76 games because, I mean, the guy is human. (Theoretically.)

Matt Wallner
I feel a little bad for Wallner, because his incredible rookie campaign was so largely overshadowed by those of Julien, who showed up in the Rookie of the Voting, and Lewis, who starred in the postseason. In any other season there would have been a lot more chatter surrounding Wallner, the reigning Minor League Player of the Year who broke through with a .249/.370/.507 slash line in 76 games for the Twins, sprinkling several highlight reel splashes into his 14-HR outburst.

What does regression look like?
In some ways, Wallner feels ripest for regression of this bunch. He doesn't have the consistent track record or floor-raising patience of Julien. He doesn't have the No. 1 pick pedigree or magical aura of Lewis. Wallner whiffs a lot and strikes out in bunches, which can cause some consternation. 

At the same time, he has some really durable underlying skills and traits that don't necessarily lend themselves to a fade. He hits the ball incredibly hard, with consistency, and while he strikes out a fair amount it's not like he's at Miguel Sanó or Joey Gallo levels. Wallner also has a healthy walk rate and draws more HBPs than usual with his plate-crowding stance, giving him a solid OBP floor.

In short, it's a pretty good formula for ongoing offensive success, although like Julien and Lewis, Wallner will have a hard time meeting the exceedingly high bar he's set even if he continues to do his thing.

One way or another, fans should be bracing for some level of regression from this trio, as each talented player seemed to be scratching his realistic ceiling as a rookie. How much regression is in store? That answer may play a big role in telling the story of the 2024 Minnesota Twins.