A Tale of Two ‘Seasons’ for Paul DeJong

Paul DeJong followed his breakout campaign in 2017 (due at least in some part to a .349 BABIP), with a solid 2018 (103 wRC+) that proved he could be a valuable asset to the Cardinals. His bat and glove are both crucial parts to the team and this appeared to be the case in 2019 as well. As a result of his strong start to the season, DeJong was added to the All-Star Game roster as St. Louis’s lone representative. However, after his appearance in the Midsummer Classic, DeJong’s production nosedived in the second half. (In fact, he truly only had one great month this season, and that was the first month of the year. DeJong failed to bat over .233 in any month for the rest of the season.)

In order to determine what went wrong, I will look at his first half and second half results separately. Even though DeJong struggled in May and June as well, when these months are combined with his production from the first half of the season, his overall line is slightly above his career average. Since DeJong’s numbers were relatively in line with his career averages by the half way point of the season, this provides a good data sample with which to compare his second half numbers, as May and June can simply be seen as a natural regression from his first month of the season. Nonetheless, it seems unlikely that this was the case in the second half of the season.

By the time the All Star break came around, DeJong had posted a 108 wRC+ on a pretty normal, if even a bit below average .291 BABIP. However, in the second half of the season, these numbers dropped considerably as the Cardinals shortstop hit his way to a 90 wRC+ and a .210 BABIP in the final three months of the 2019 season.

DeJong’s second half BABIP of .210 suggests that there is plenty of room for positive regression, but this is not the biggest supportive detail of what was a subpar second half at the plate. DeJong’s walk rate stayed relatively constant throughout the season as he walked at a rate of 9.6 percent in the first half and nine percent in the second half; his strike out rate, on the other hand, did not remain constant. DeJong fanned at a healthy rate of 19.1 percent in the first three months of competition, which was much improved from the 25.1 percent K% he posted in 2018. Those strike out problems that lingered throughout 2018 returned in the latter half of 2019 as whiffed 26.7 percent of the time in the final three months of the year. This begs the question: Did DeJong simply regress to his normal strike out rate in the second half of the season, or did he make improvements in the first half and simply slumped in the second half? This question will be difficult to answer until we see what DeJong does in 2020.

Over the course of the entire 2019 season, the 26-year-old DeJong swung at a higher percentage of pitches than the year prior. (O-Swing% increased by 1.3 percent and Z-Swing% by 4.8.) It is an encouraging sign that DeJong was able to be more aggressive at the plate, while walking at a similar rate and swinging through pitches at a lesser rate. This increased aggressiveness could have caused DeJong to swing at worse pitches and thus, have weaker contact. Either way, it is difficult to determine which DeJong is the real DeJong in terms of plate discipline — the first-half version or the second-half version.

There was also a significant change in DeJong’s batted ball results in the two halves. In the first half of the year, DeJong posted a 20.8 line-drive percentage. DeJong hit ground balls nearly 37 percent of the time and fly balls at a rate of over 42 percent. This changed drastically in the second half. DeJong’s line-drive rate collapsed to 13.9 percent and his groundball percentage rose to nearly 39 percent while his flyball rate rose to 47.2%. This drop in line-drive rate corresponds to a major drop in batting average in the second half of the season and would help explain why DeJong’s BABIP was so low, besides bad luck.

Line drives are the best result for a hitter, in terms of batting average. While fly balls lead to more home runs, line drives are as close to guaranteed hits as it gets for a hitter. In 2018, the BABIP on fly balls was just .117. While fly balls lead to home runs, they also lead to a lot of outs because a ball that hangs in the air is easy to catch if it stays in the park. On the contrary, the league-wide BABIP on line drives was .672 (ground balls were at .236). This makes it pretty clear as to the effects that a nearly seven-point decrease in line-drive percentage would have on DeJong’s second-half numbers. There was likely still an element of bad luck, but the 13.9 percent line-drive rate DeJong posted played a significant role in his second-half fade as well.

The good news for DeJong is that it appears his second-half batted ball numbers were a fluke. DeJong’s career-average line-drive percentage is 21.4, much higher than the 13.9 percent in the second-half of the season. It appears that it would be much more likely in the long term for DeJong to maintain a rate similar to the 20.8% that he enjoyed in the first half of 2019.

Interestingly, DeJong actually hit more home runs in the second half of the season, despite his slump. After hitting 13 balls over the fence in the first half of the season, DeJong clubbed another 17 home runs after the All Star break. However, this makes sense considering DeJong’s 4.9 percent increase in flyball rate. DeJong’s HR/FB ratio was hovering around 11.8 percent before the All Star break; after the break, it shot up to 20 percent.

This is about the only positive change that DeJong experienced in the second half of the season, and it kept his season numbers from declining below a 90 wRC+. In fact, DeJong’s ISO rose drastically after the break: from .185 to .245. Without this, DeJong’s second-half stat line would have looked significantly worse. DeJong should be able to reset at the beginning of next season and get back to hitting the ball like he knows how.

DeJong’s increased strikeout rate in the second half of 2019 is likely to decline, while his line-drive rate should return to normality next season. It is unlikely that DeJong has become a hitter who strikes out at a 26.7 percent rate and hits line drives on only 13.9 percent of the pitches he makes contact with. These two stats drove his second half struggles, but are unlikely to be maintained throughout the several seasons to come in DeJong’s career.

A return to career-average levels would allow DeJong to provide plenty of value with his slightly above average bat and accolade-worthy glove.