The breakout season of Bobby Witt Jr. explained in three stats

Across his first eight playing months as a major leaguer, Bobby Witt Jr. was an adequate, if not a pretty player. According to Fangraphs, once a player gets into the 2-3 fWAR range, they are a solid starter compared to their peers. Since 2018, only five Royals have been worth more than 2.0 fWAR. Bobby was one of those Royals as a rookie in 2022, despite struggling on defense and being a slightly below-average hitter.

Through the first two months of this season, Witt was 50th in fWAR at 1.2. He was on pace for another >2.0 fWAR season thanks to a major defensive upgrade and 17 stolen bases, but his 83 wRC+ left much to be desired. Adequate, if not pretty good. But not what the Royals need from the biggest prospect in its 55 year history.

We all know what happened next. Since June, Bobby has not just showed that he is a very good player. He has flatly been one of the best players in baseball. His 3.7 fWAR since June is 6th among all MLB players, thanks to his Gold Glove defense being met with a 149 wRC+. If we track since the All-Star break, it’s even better. His wRC+ kicks up to 176 and no player has been more valuable, although Julio Rodriguez is making a run at him.

For the season, his fWAR stands at 5.1 good for 6th best. For a day, he was 5th best. The Royals haven’t had a player finish top five in fWAR since George Brett in 1985. Only five Royals since 2000 have finished the season with an fWAR north of 5.0 and Bobby still over a month to go.

He’s having one of the best individual seasons in Royals history despite middling for the first two months.

So what changed? Truthfully, not a lot.

He was hitting the ball hard, even as he struggled. However, there are a few noteworthy improvements we’ve seen this season that help explain his sophomore jump.

Strikeout Percentage

This is the most obvious improvement between the last three months and the first two months. Generally speaking, as home runs go up, strikeouts go up. The most Salvador Perez has struck out in his career was 2021, when he hit 48 homers. The highest strikeout rate of Eric Hosmer’s career in Kansas City came when he set a career-high in homers. This isn’t always true, of course, but it is often true.

Witt has always been vulnerable to the strikeout. We knew he would be coming out of high school. His hit tool was his weakest tool. And he has already hit more homers this season than he has ever hit as a professional. However, not only are his strikeouts down, but he is striking out less often than he has ever struck out at any level.

In his monster 2021 season across AA and AAA, Witt struck out 23% of the time. He struck out 21% of the time last. This season, with an uptick in power and with his chase rate and swing rate staying mostly the same, he’s striking out just 18% of the time.

That’s not just good for Bobby, but in the 75th percentile across all of baseball. His 18.5% K% ranks 95 out of 138 qualified hitters. As of of May 31, he was striking out 22.8% of the time, the 63rd highest percentage in baseball, slightly below league average. Since June 1, only 20 of 151 qualified hitters have struck out less than him.

If anything, this development shows that the concerns over his bat-to-ball skills were a bit exaggerated. Either way, he’s hitting more homers and striking out way less, a somewhat rare combination.

Fastball Runs Above Average and Pitches up in the Zone

Last year was noteworthy for Witt’s struggles with the fastball. He was worth -2.6 runs above average against four-seamers and a combined -7.8 against four-seamers and sinkers.

Through May of last season, he was worth -7.6 runs against four-seamers alone. That has changed this year. According to Baseball Savant, Witt has been worth 15 more runs against fastballs this season than he was last season, and 25 more runs if you include cutters and sinkers. That’s not to mention his destruction of changeups this season.

Equally notable has been Witt’s turnaround against pitches up in the zone. The rates here are limited to pitches in the strike zone, for the sake of my own time. But the differences are arguably more extreme than his improvement against fastballs.

It is apparent that Witt didn’t have a physical limitation against fastballs or pitches up in the zone, as his hands and bat speed are among the best in the league. While frustrating, those always seemed to be a fixable problems. That has proven to be true. But ultimately, neither of these things are the biggest improvement to Witt’s game.

Outs Above Average

Much was made of Witt’s defensive struggles last year. However, as pointed out by David Lesky’s piece last October, there was probably more to the story, and splitting time between shortstop and third did not help.

Like he did cutting down his strikes, Bobby not only improved, but he made himself one of the league’s best. After ranking in the second percentile of OAA in 2022, Witt ranks in the 100th percentile this season.

He also has the seventh-best defensive runs above average in the all of baseball and the highest figure among shortstops. It would be good for the fifth-best defensive season in Royals history among shortstops, with only Nicky Lopez, Tony Pena Jr (!!), and Alcides Escobar having better individual seasons.

His nine errors on the season are light work compared to the 19 he committed last season. In fact, he committed 16 errors at shortstop alone, seven more than he has this season and in nearly 200 fewer innings.

There are more numbers showing Witt’s leap from a good starter to a superstar this season. And to a degree, they all show us something we already knew. He made his Major League debut with 744 professional plate appearances to his name. He never stepped in a collegiate batter’s box. He was going to be raw.

But in just a season, we are seeing that rawness fall away rapidly. He has taken what were weaknesses and turned them into league-best strengths in some cases. There is no guarantee that this continues, but I think most would agree Witt is here to stay. Now the question is, where is the ceiling?