What’s gone wrong for Tony Gonsolin this season

Entering the season the Dodgers were expected to have a three-headed monster at the top of their rotation in Clayton Kershaw, Julio Urías and Tony Gonsolin. However, that’s been anything but the case. Kershaw has been fantastic this season pitching to a sparkling 2.55 ERA, but he hasn’t pitched June 27 due to a shoulder injury. Urías has battled injuries throughout the season and he has a brutal 4.98 ERA (4.17 xERA) in his 81 ⅓ innings pitched.

Gonsolin, though, feels like he’s been the biggest disappointment of the group. He didn’t debut until April 26 due to an ankle injury he suffered in spring training, and when he’s pitched he’s been poor. The former All-Star has pitched to a 4.25 ERA (4.84 xERA) and is striking out just 19.7 percent of batters he faces compared to a 9.6 percent walk rate. His drop in performance continuing this deep raises the question of was he lucky last season, has he been unlucky this season or is this just who he is?

Was he lucky last season?

Gonsolin was certainly a lucky starter last season, but even if he pitched to his expected metrics he still would’ve been an elite pitcher. His xERA of 3.12 was nearly a run higher than his actual ERA of 2.14 and his xwOBA of .276 was considerably higher than his wOBA of .238. For reference as to how good those expected metrics are, Spencer Strider, one of if not the favorite for the NL CY Young this year, has an xWOBA of 2.75 and xERA of 3.10. They are of course different pitchers, but Gonsolin last season was effectively Strider this year.

His left on base percentage was a bit high at 83.8 percent and his home-run-to-fly-ball rate of 8.2 percent was slightly low so yes there was a little luck there as well. Although, it was nothing like Trevor Bauer’s left on base percentage of 90.3 percent in his Cy Young season with Cincinnati.

As a result of all those numbers we certainly should’ve expected a step back in Gonsolin’s game but not one of this magnitude.

Is he unlucky this season?

No, not at all, in fact, Gonsolin has actually been rather lucky this season. He has a 4.25 ERA, which is lower than his xERA (4.84), FIP (4.82) and xFIP (5.08). Traditionally, when a player has a bloated ERA compared to the prior season we see their FIP being significantly lower as an indicator that there are better days ahead. Unfortunately, that’s not been the case for Gonsolin as highlighted by the numbers above. On top of those expected metrics he also has a BABIP of .221 which is a number that will likely go up over time which will result in even worse back of the baseball card numbers.

So what’s gone wrong this year?

This is where things are a bit weird for me as there are very few metrics that can explain the drop off in his game. Outside of his four-seam fastball which has seen its spin rate drop 102 RPM, which isn’t a massive difference, his curveball, slider and split-finger are all nearly identical from last year’s numbers. Additionally, his four-seam is moving the most it ever has this season with a 1.8 inch uptick in vertical movement and 2.5 inch bump in horizontal movement. His splitter has also seen a similar increase in movement with his curve and slider not moving much in either direction. His pitch velocity has also not seen a drop that would cause this kind of regression is his numbers.

His quality of contact numbers have seen a slight change but not enough to make me overly concerned. His average exit velocity is up only 0.1 MPH from last season, his pop up percentage has gone up 2.4 percent which should help his metrics and his fly ball rate has gone up just 2.2 percent. Yes his ground ball rate has gone down four percent, but it’s largely offset by his increase in pop ups induced. Additionally, his weak-contact percentage is 4.6 percent, a 1.2 percent increase from last 2022 and his solid contact percentage is 4.6 percent which is lower than last year’s number.

The only quality of contact metrics that would indicate regression this season is his barrel and hard hit rates. His barrel rate is at 8.9 percent, a 3.3 percent jump and his hard-hit rate has increased from 35 to 38.8 percent which explains his xwOBAcon (xwOBA on contact only) going from .327 to .376.

With all that considered though there are three numbers to me that explain his fall off in 2023:

• Over the last three seasons his whiff percentage has gone from 29.7, to 26.9 and all the way down to 21 percent this season.
• His chase contact rate in 2021 it was 46.2 percent, and in 2022 it was 51.3 percent. This year, it’s 63.8 percent, a number that’s 5.7 percent higher than league average.

Gonsolin’s zone contact rate last season was 81.6 percent, this year it’s 86.7. So essentially, Gonsolin is missing fewer bats in 2023 which is an indicator that his stuff isn’t nearly as good this year.

Is there hope?

For this season, not really. There isn’t a single metric that indicates Gonsolin is going to improve this season, and if anything we should expect him to get worse over time. Now, is it possible the former All-Star is battling through an injury and will improve next season? Of course. There’s definitely a chance that Gonsolin gets back to his 2022 form next season, but we shouldn’t expect it.