As I am sure few would argue, Christian Yelich has demonstrated one of the highest ceilings in franchise history. However, despite the disappointment of the last few years, it's important to pick out why he's been struggling.

First off, let's dive into what the stats say has changed for Yelich since that infamous knee injury, first looking at the 2020 season, why it wasn't as bad as we thought, and then the following years where the back has possibly played up a little more.

2020

In 2020, he had a career-high average exit velocity of 94.0 mph, a hard hit rate of 55.6%, and a walk rate of 18.6%, which doesn't scream the "declining peripherals" of someone whose knee injury has demolished him. His launch angle on average was 7.1 degrees, which, to give context for him personally, his average launch angle was just 5 degrees in his 2018 MVP year.

So why did 2020 feel like a down year for Yelich? Well, there's a straightforward answer: he started to whiff on fastballs, but with secondary pitches too. In 2018 and 2019, Yelich had no weaknesses for any pitch, hitting well across all areas of the strike zone. Yet in 2020, he couldn't hit anything other than a four-seam fastball and a slider. Every other pitch had a batting average below the Mendoza line and a slugging % below .370. Even with his better pitches, his whiff rate increased massively; in 2018, Yelich's whiff rates on fastballs and sinkers were 12.6% and 11.2%, respectively; in 2020, this increased to 26.9% and 22.2%.

2021

In 2021, Yelich had some back issues during the season, but his swing started to regain some control over fastballs again, dropping to a whiff rate of 18.8% and 10.6%, respectively, for four-seam fastballs and sinkers. However, the power wasn't there, particularly against breaking balls hitting .228/.246 in PAs finishing on the slider and hitting .105/.158 in PAs that finished with a curve. At times, it's looked as though his timing could have been better, able to foul off the fastballs but not barrelling them up. To back up the eye test, his most considerable power output has come against the change-up in the last two seasons, hitting to the tune of .274/.581 against it in 2021.

2021/2022 Pitch Breakdown

2022

In 2022, his whiff rate stayed below 20% on both four-seam and two-seam fastballs, but he increased his batting average and xBA by over .030 points, recording a .307/.469 against the four-seam version and a +12 run differential. He also took a big step forward against the slider, hitting .250/.398 but struggled with the curveball at .125/.188 and took a step back against the changeup, albeit with power as he hit .224/.466 against the pitch. His ground ball rate was 59.1% and had been increasing each of the last two years, with a particular propensity for contact classified as "weak" or "topped," a lot of which have come against breaking balls (backed up by his 2021 xBA against them of .210, xSLG of .211). However, in 2022 he did take a step forward in launch angle against breaking balls, allowing him to create a bit of power when he did make quality contact against them. 

To look deeper into the curveball issues, from watching the past few years, he has an issue picking up the curve when it's thrown to him, regularly chasing it as it drops well below the strike zone. It's an area pitchers are targeting, with 31.8% of a pitcher being thrown at him outside the zone in the lower half. He creates a lot of line drives and hard contact, with five of the nine zones producing average exit velocities over 95mph, and in the middle/upper half of the strike zone, he creates a high number of line drives. The issue is pitching in the bottom third or below, where his highest line drive percentage is 15%, yet contrast this with a few inches above that, where he manages 36% line drives. Below the zone, he whiffs 71% & 61% of the time vs. his ability to foul off pitches above the zone, to whiff rates at 36% and 25%, and a pattern begins to emerge. A vast, glaring weakness that he's facing, and one the curveball perfectly exploits, also is a leading cause in his ground ball rate. On pitches down and middle or down and away (In zone), the launch angle averages at -5 degrees, and this only worsens as the pitches drop out of the strike zone.

2022 K%/Whiff %

He has the same swing that could cover every pitch, so it's possible that either through overthinking his approach, or the back injury in 2021, he's gone back to an approach that's been more engrained in him from his days with the Marlins. One big difference is in the 2019 vs. 2022 comparison; his whiff rate on curveballs (45.6% vs. 37.6%), sliders (46.6% vs. 32.7%), and changeups (39.1% vs. 33.9%) tell us that Yelich is potentially swinging more conservatively and taking less of a cut at pitches to maintain maybe a longer/higher quality AB, and would go a way to explain his decrease in average exit velocity from 94 mph to 91mph. However, for comparison's sake, it's also important to note that O'Neil Cruz had a similar average exit velocity at 91.9mph last season.

In terms of his "run value" from his swing/take decisions, specifically focusing on the heart of the plate, look at the comparison between 2018/19 vs 2020-2022. A more aggressive approach in terms of what he swings at seems to pay massive dividends in results for him:

His line drive rate in the lower part of the zone appears to be an area of weakness that has only sometimes been there, and it may be a timing issue rather than back-related. However, back injuries can have an impact in a variety of ways. If he can get a handle on even picking and laying off those low curveballs and pitches below the zone, we could see a dramatic improvement in his production this year.

It's important to stress that it's a small area, targeted heavily, having the most significant impact on Yelich's performance, and it's not an all-encompassing weakness across the board. His ground ball rate is a product of pitchers targeting the weakness down in the zone, and the question for 2023 is - can he neutralize them? 

Should Yelich embrace a bit of swing and miss to utilize his power more often?