Joc Pederson’s Ugly Second Half
For the first three months of last season, Joc Pederson looked like a future star. At the All-Star break, Pederson was hitting .230/.364/.487 and his 137 wRC+ placed him 12th among National League batters. In the last 20 years, the only players younger than Pederson to hit 20 home runs faster than Pederson (95 games) are Albert Pujols, Adam Dunn, Giancarlo Stanton, Carlos Correa, and Chris Davis, per Baseball-Reference’s Play Index. In the second half, however, things unfolded quite differently: Pederson recorded 219 terribly unproductive plate appearances, leading to questions about whether the league had figured Pederson out.
Pederson’s strikeouts rose as steadily as he did through the minors, topping out at 27% in his last Triple-A season in 2014 before he was promoted to the majors. The rise in strikeouts was accompanied by a a rise in walks and power, and that pattern continued in the first half of last season with a 16% walk rate and a 29% strikeout rate. Pederson’s first half surge did not last into the summer months, as both his BABIP (from .282 to .232) and ISO (from .257 to .122) plunged — although his walk and strikeout rates remained unchanged.
While it would be easy to point to Pederson’s BABIP decline and hope for a turnaround, there are too many other peripheral statistics that point to a general drop in Pederson’s ability last season. Pederson’s line-drive rate dropped from 18% to 14% from the first half to the second half, his infield-fly percentage went from 10% to 23%, and his soft-contact percentage moved from 15% up to 29% in the second half. His exit velocity was 93.5 mph in the first half, ranking behind only Giancarlo Stanton, Yoenis Cespedes, Ryan Braun, Miguel Cabrera, and Jorge Soler among players with 100 at bats. In the second half, however, it dropped to 89.3 mph, per Baseball Savant.
Although Pederson’s strikeout rate remained unchanged, it would not be fair to say that his approach did the same. Pederson recorded the fourth-highest rate of pitches per plate appearances on the season (4.2), behind only Curtis Granderson, Joey Votto and Matt Carpenter in the National League, but he actually saw more pitches in the second half than he did in the first. The types of pitches he saw did not change too much, as this chart from Brooks Baseball shows. (Note: October’s sample amounts to just five plate appearances.)
Pederson did see a few more sliders in the second half, especially with two strikes (20.6% in the first half, 23.9% in the second half), but the difference had less to do with the pitches seen and more to do with what Pederson was doing with the pitches. Over the season, he saw more four-seam fastballs and sliders than any other pitches. His swing and whiff rates on the four-seam fastball remained roughly the same from the first half to the second half, but on the slider, particularly with two strikes, the numbers moved up considerably, per Brooks Baseball.
| 1st Half | Sw% | 2-strikes Sw% | Whiff/Sw% | 2-strikes Whiff/Sw% | |
| 1st Half | Fourseam | 40.1% | 48.6% | 36.4% | 28.6% |
| 2nd Half | Fourseam | 42.6% | 52.0% | 37.5% | 28.8% |
| DIFFERENCE | 2.5% | 3.4% | 1.1% | 0.2% | |
| 1st Half | Slider | 50.5% | 55.8% | 42.1% | 31.2% |
| 2nd Half | Slider | 53.9% | 70.8% | 44.0% | 37.3% |
| DIFFERENCE | 3.4% | 15.0% | 1.9% | 6.1% |
When Pederson was thrown a slider with two strikes in the second half, he swung more than two-thirds of the time, and he did not make a lot of contact. These numbers were up significantly relative to the first half. While it would also be easy to say that the league figured Pederson out, it could be that it was Pederson who changed.
Fatigue cannot be ruled out as part of Pederson’s second-half issues. He was in the middle of his first full major-league season, and the Dodgers rode him very hard in the first half. Of the Dodgers 90 first half games, Pederson played in all but one of them, receiving a day off after a stretch of 12 games in 11 days in early June. He started 55 of the team’s first 58 games and, by the end of July, he had played in 101 of 102 games, starting 95 of those.
Pederson’s rough second half has dampened much of the enthusiasm surrounding Pederson, but overall, he had a successful first season. His batting average ended as an ugly .210. A 16% walk rate, however, led to a solid .346 on-base percentage — and his .417 slugging percentage helped him post a solidly above average 115 wRC+ on the season. We don’t know if his first half or second half is more real as far as future expectations go. Steamer sees them both as real, essentially forecasting a repeat of Pederson’s 2015 season.
Pederson is not the first rookie to have a solid first half followed by disappointment after the All-Star break. Pederson experienced a 58-point drop in wRC+ from the first half to the second half. Over the last dozen years, a handful of players have posted similar drops and still managed to put up above -verage offensive seasons (min. 150 PA in each half). Below are the players since 2002 to have an above-average first half followed by a below-average second half with a drop of at least 30 points in wRC+.
| Player | Year | 1st Half wRC+ | 2nd Half wRC+ | DIFFERENCE |
| Mike Napoli | 2006 | 157 | 68 | -90 |
| Evan Gattis | 2013 | 136 | 84 | -52 |
| Anthony Rendon | 2013 | 127 | 77 | -49 |
| Ian Kinsler | 2006 | 133 | 85 | -48 |
| Andre Ethier | 2006 | 143 | 99 | -44 |
| Dan Uggla | 2006 | 125 | 95 | -31 |
Pederson fits in pretty well with the above group. Here is how those players did in their first three years.
| Player | Rookie wRC+ | 2nd Year wRC+ | 3rd Year wRC+ | Year 2 and 3 AVG | Diff of (Year 2 and 3) and Rookie wRC+ |
| Mike Napoli | 115 | 109 | 146 | 128 | 13 |
| Evan Gattis | 110 | 126 | 99 | 113 | 3 |
| Anthony Rendon | 100 | 130 | 97 | 114 | 14 |
| Ian Kinsler | 102 | 108 | 133 | 121 | 19 |
| Andre Ethier | 117 | 104 | 134 | 119 | 2 |
| Dan Uggla | 110 | 106 | 126 | 116 | 6 |
| AVERAGE | 109 | 114 | 123 | 118 | 9 |
Every player did the same or better over the next two seasons relative to their rookie years. A second-half slump is far from dooming a career, particularly when the first half is so good. Going back a little further using the Baseball Reference Play Index, here is another, near perfect analog to Joc Pederson:
| HR | BA | OBP | SLG | sOPS+ | |
| 1st Half | 20 | 0.313 | 0.361 | 0.543 | 146 |
| 2nd Half | 2 | 0.257 | 0.330 | 0.335 | 87 |
Wally Joyner would go on to average a 124 wRC+ over the next four seasons. Pederson’s poor second half does bring up questions about his ability to hit major-league pitching going forward, but given the possibility of fatigue and the need to make adjustments to major league pitching, Pederson’s first half and his overall line say a lot more about his potential than his difficult second half. With only one season to go on, and the most recent sample a poor one, Pederson’s star might have faded a bit, but judging his future on just 200 plate appearances is not very sound.
Craig Edwards can be found on twitter @craigjedwards.
Good breakdown.
I would like to relay some speculation regarding his second-half slump. Quite a few people have suggested that Pederson, due to his unusual offensive skillset, especially for a centerfielder, has been a victim of “fixing what ain’t broke.” Even when crushing the ball in the first half, there were a lot of people who were wringing their hands about his high strikeout rate – some of them worried about what it meant for his future, others simply refusing to believe that he could be a valuable hitter despite having a .390 OBP and over .500 SLG at the time. I have no insight into the type of input he was getting from coaches, so I’m not putting this forward as a well-evidenced theory, but I have heard this from various sources. The content of this article is consistent with this theory though; it looks like the league may not have pitched him all that differently, and it is he would adjusted, perhaps when he didn’t need to. He seemed to get more defensive with two strikes, something every half-baked hitting coach that called into Dodger Talk thought he should do.