Jason Heyward arrived in 2010, and he arrived. In his age-20 rookie season, Heyward hit to the tune of a 134 wRC+. Among all age 20 rookie seasons going back as far as FanGraphs can go, it's the 10th best by wRC+. Using an arbitrary 300 PA cutoff, his rookie season wRC+ becomes the 6th best among 20 year old rookies. Unfortunately, that has proven to be his best offensive season in his young career. Heyward has been on a bit of a downward trajectory since then.
Sometimes, in a down season, performance issues can be related to struggles with handedness. Let's look at some handedness splits!
Dude's a righty crusher, for sure. His 2014 wRC+ against RHP is the same as his career value, so I think it's safe to say that Jason Heyward is a very good hitter against RHP.
However, against lefties, Heyward has shown significant variation. His single season wRC+ against LHP ranges from 28 this year to 125 last year. That's a much larger range than against RHP. Small samples sizes do apply here, though. It takes at least 1,000 PA against each hand for platoon splits to stabilize.
Then again, Heyward has 807 PA against LHP, and if he stays healthy, he'll have another 50-100 PA by the end of this season against LHP. He's still under that 1,000 PA threshold, but he's getting closer. At some point soon, we can probably conclude that Jason Heyward's platoon split is for real, but it's nothing more than average. In fact, in 2014, the league wRC+ for left handed hitters against LHP is 82, which is Heyward's career value. Heyward is worse against lefties, but he's no worse than average so far. His poor 2014 performance is dragging down his career numbers, and it's possible that the BABIP variation is responsible.
Given that Heyward has significant variation in performance against lefties and still has a bit too small of a sample size against lefties, it's too early to determine if his bat is a platoon bat. However, this completely ignores another significant aspect of Heyward's value: his defense. He is easily an elite defender patrolling RF, such that his defense could make up for any deficiency of his bat against lefties. Also, don't forget that as a left handed hitter, he has the larger side of the platoon anyway.
Right now, and while Heyward is in his prime, Heyward will likely be too good to be relegated to platoon duty. He is still very young. In his 30s, maybe a normal aging curve will force Heyward into part-time duty. That's a long way away.
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All statistics courtesy of FanGraphs.
Kevin Ruprecht is a Featured Writer of Beyond the Box Score. He also writes at Royals Review. You can follow him on Twitter at @KevinRuprecht.