Will The 2023 Rookie Class Suffer A Sophomore Slump?

The Brewers called up several exciting rookies in 2023. Some sported mullets, some threw wicked sinkers with triple-digit velocity, some were defensive experts, and several took up metaphorical spaces only slightly less extreme. In a sport as multifaceted as baseball, it’s always challenging to try and predict whether rookies will sustain their early successes, but it’s fun to do so, anyway.

Image courtesy of Brewer Fanatic & Brock Beauchamp

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Joey Wiemer
Wiemer burst onto the scene with a 64” frame and á wacky swing, making his debut on April 1st after just missing out on the Opening Day roster. Ranked as the team’s third-best prospect and the 90th overall by MLB Pipeline, Wiemer came with some noticeable prospect hype. His first two months were paltry at best, with a .678 OPS in April and a .497 OPS in May. He found his groove in June, slashing .233/.337/.512 across 101 plate appearances, but he couldn’t hold onto that magic. He closed out the campaign with a .505 OPS in August and a .438 OPS in September. While Wiemer was included on the Brewers’ postseason roster, he did not have a plate appearance in the Wild Card Series.

A noisy swing was the main culprit, fueling exceptionally high whiff (33.6%, 9th percentile) and strikeout (28.3%, 17th percentile) rates. He also struggled immensely with hitting breaking balls, accumulating a run value of -11 against sliders, the pitch he saw most frequently. He also accumulated a -4 run value against the curveball and sweeper. When he did make contact, he struggled to achieve a valuable launch angle, finding the sweet spot at an alarmingly low rate (28.9%, 6th percentile).

On the bright side, Wiemer had two great qualities: defense and hustle. His sprint speed was in the top 11% of the league, and that (combined with his excellent arm strength (89.3 mph, 81st percentile)) allowed him to be an exceptional defender in center field. He accumulated 7 Outs Above Average and 5 Defensive Runs Saved.

Whether Wiemer improves next year depends on whether he can kick existing bad habits. If he can use this offseason to correct his swing and approach at a place like Driveline, he might have a chance to be one of the most well-rounded outfielders in MLB. If nothing changes, he might struggle to find consistent playing time on the Brewers, a team stacked high with outfield talent. Sure, he’s a defensive asset, but based on how Milwaukee performed at the plate last year (.704 OPS, 23rd in MLB), they’ll trade a few outs on balls in play for significantly more production at the plate any day of the week.

Abner Uribe
Uribe was one of the most electric pitchers on Milwaukee’s staff, and for a squad that included the likes of Brandon Woodruff, Corbin Burnes, Devin Williams, and Freddy Peralta, that’s saying a lot. With a lethal sinker that averaged 99.4 mph and a slider that averaged 89.4 mph, he posted an ERA of 1.76 and a WHIP of 1.17 over 30 2/3 innings pitched.

His slider became an especially effective weapon, boasting outlandish strikeout and whiff rates of 62.1% and 58.1%. Opposing batters averaged just .080 against it, and the xBA (expected batting average) was even lower, at a measly .028. These excellent metrics can be attributed to the unreal amount of movement on the pitch. With 32.2 inches of vertical drop and 8.6 inches of horizontal break, and given the sheer velocity of the fastball off which the pitch plays, it’s no wonder it often leaves hitters dazed and confused.

He struggled a little with control, posting a 15.7% walk rate and a somewhat low chase rate at just 24.2%. He was also known to give up some hard contact, with 43.3 percent of opponents’ batted balls leaving the bat at 95 miles per hour or more. His Statcast xERA (expected earned run average) was 3.53, significantly higher than the 1.76 he ended up with. His FIP (Fielding Independent Pitching) of 2.77 also signaled that he may have gotten a little luckier than most in 2023, though both those gaps can also be attributed to good defense behind him.

Uribe’s raw talent is undeniable. With a full offseason of work in the Milwaukee pitching system, fans should be confident that he’ll return better than ever, barring injury...