The curious case of Cody Bellinger’s rebound

Cody Bellinger has been one of the hottest players in baseball over the last 30 days. The Cubs centerfielder and first baseman is slashing .436/.461/.713 with seven home runs, two stolen bases and a wRC+ of 215 over that time period. Every time I turn around and see the Cubs coming back from a deficit or taking a lead early, Bellinger is right in the mix. The calls on Twitter to extend one of the Cubs best players, who just turned 28 on July 13, have gotten louder, but as with everything dealing with the 2023 Cubs the numbers behind Bellinger’s rebound are, well, complicated. With the trade deadline just a week and a day away I wanted to dive into Cody Bellinger’s rebound and see if we could come up with some answers.

The Cubs signed Cody Bellinger after the Dodgers non-tendered him this winter rather than pay him the $20 million he was due in arbitration. They signed him to a $17.5 million/one-year deal (it’s a $12 million base salary with a $5.5 million buyout on a mutual option for 2024 that will almost certainly not be exercised). I described that deal as a low-risk, high-upside play that would improve the Cubs defensively and give Bellinger his best shot to reestablish his offensive value before hitting the free agent market:

He’s still ever so slightly above average at barreling the baseball (54th percentile, according to Statcast). If (and it’s a big if) the swing work he’s doing this offseason gets him back to a league average bat, it’s a plus. If it gets him back to an above average bat, as that improved wOBA against fastballs suggests, there’s an outside chance the Cubs got quite the deal to help them compete in 2023. Worst case scenario, if the rest of the offseason doesn’t come together, half a year of an even partially rehabilitated Bellinger should net Jed Hoyer and company a pretty nice return at the trade deadline. It’s certainly worth $17.5 million to find out.

Well, it turns out that Cody Bellinger did have something left to demonstrate on the field offensively, and honestly he couldn’t have timed it any better to showcase his best stuff before the deadline. The thing is, he’s bringing an underachieving Cubs team right along with him. As I write this on an off-day, the Cubs are 48-51, 6½ games out of the NL Central division lead and 5½ games back of a Wild Card spot. They’ll play two games against the White Sox on the South Side and then four more against the Cardinals in St. Louis — the two teams who, while struggling, would love nothing more than to make the Cubs sell at the deadline. A lot of decisions hang in the balance of those games, but perhaps none is as intriguing as whether the Cubs should trade, retain, or maybe even extend Cody Bellinger.

Statcast

When I wrote about this trade in December I noted that Bellinger still had a 54th percentile barrel rate. For those who don’t spend all their free time in Statcast data, barrel’s are balls hit at a certain exit velocity and launch angle such that similar batted ball events have a .500 batting average and 1.500 SLG. In other words, these are balls that are supposed to be extra base hits more often than not. In looking at Bellinger’s slashline and results you’d probably presume his barrel rate had improved. You would be wrong:

Baseball Savant

In fact, that 29th percentile correlates with the worst barrel rate of Bellinger’s career. He currently barrels the ball 6 percent of the time. That’s down from 12.6 percent off his MVP season in 2019 and it’s been a steady downward slide. Below you can see Bellinger’s barrel rate, hard hit rate and strikeout rate by year:

It isn’t just the barrel rate. Bellinger’s hard hit rate is also at a career low. And not like a “oh it’s kind of similar to some other year where he was pretty good” low, like a cratered out, 3 percent worse than the abysmal 2021 season that represented the nadir of the Bellinger fall from grace. Another way to visualize this data is in the 15-game rolling graphs at FanGraphs, and you can see that Bellinger’s hard hit data has tracked with his wOBA (fancy on-base percentage that gives you more credit for extra bases) pretty consistently — until 2023:

FanGraphs

It’s a bit of a mystery, until you look at a different number that honestly shouldn’t be that predictive of this Bellinger rebound on it’s own, and yet, seems to be inversely correlated to Cody Bellinger’s highest wOBA’s throughout his career — his K rate:

FanGraphs

When Bellinger is striking out less, his wOBA explodes. When he’s striking out more, his wOBA collapses. At least for now in Bellinger’s case, striking out at around 17 percent of the time as opposed to the 25+ percent of the time appears to be making a huge difference.

BABIP

But that doesn’t really clarify things all that much. Let’s introduce one more variable into the equation, BABIP. Bellinger’s career BABIP is .283. During his 2019 MVP campaign he got that number up to .302, and he posted a to that point career-high .313 BABIP during 2018 — in 2023 Bellinger’s BABIP is .338.

Now, under normal circumstances I might look at that number and consider it luck. A fluke that will sort itself out of the course of a season, because, baseball. But 2023 isn’t normal circumstances. 2023 has new shift rules, and Bellinger has always been a pull-side power sort of guy. While there is a chance his high BABIP is luck-based, there is also a chance it’s the result of rule changes that created a more friendly hitting environment for guys just like Bellinger.

Takeaways

It’s a bit of a conundrum for the front office types at the corner of Clark and Addison. On the one hand, they’ve gotten exactly the rebound they hoped for from Bellinger and with the Cubs sitting at a 12.5 percent chance to make the postseason according to FanGraphs, the smart move is to trade new-peak Bellinger for whatever prospects could help the next great Cubs team and let some other team sort out the noise in the Statcast numbers and rule changes. On the other hand, this Cubs team is better than that 12.5 percent chance for a number of reasons I’ve covered before. They are still the only team in the NL Central with a positive run-differential, and at +41, they have the fourth best run-differential in the National League. The starting pitching has been a strength, the bullpen is coming together and the second half schedule is not nearly as tough as the first half was. After two years of Jed Hoyer’s fire sales, the players have demonstrated they can compete in this weak division, and shouldn’t a team like the Cubs build around Bellinger’s rebound and make a run at extending him in the offseason if the numbers hold?

It’s a difficult set of data with about a week and a day for Hoyer & Co. to make a decision. If the Cubs win out or lose out they’ll make that decision for the front office. However, for now, Cody Bellinger seems to have decided he’ll just do everything in his power to force this team into buying, rather than selling.