When the 2013 season ended, Jay Bruce was 26 and coming off of three straight 30-homer seasons. Sure, he struck out a bit much, and had some issues defensively, but he was a young man in his prime, a bankable asset, an easy way to inject power into your lineup. Since then, he’s slashed .222/.288/.406 with 22 homers per 600 plate appearances over two seasons.

What happened?

Batting average on balls in play seems like a big culprit. Just look at the last four years broken in half. So much seems the same except for BABIP.

The Last Four Years of Jay Bruce , Halved Seasons BB% K% AVG OBP SLG GB/FB HR/FB Pull% Hard% BABIP 2012-2013 9.4% 25.6% 0.257 0.328 0.495 0.86 17.9% 42.7% 36.0% 0.304 2014-2015 8.5% 24.6% 0.222 0.288 0.406 1.02 14.0% 47.7% 34.3% 0.259

Let’s ignore any small differences here or there at first, and focus on the BABIP, just because we always seem to start there. Bruce is a pull hitter (his pull rate the last two years is 23% higher than league average), and he’s a lefty. Could it be the shift that is stealing hits from him?

No, it doesn’t look like it.

Jay Bruce Shift Results Season PA Shifted Shift BABIP No Shift BABIP XBH% Shift XBH% No Shift 2015 434 174 0.276 0.195 0.081 0.073 2014 350 192 0.292 0.211 0.073 0.000 2013 418 121 0.231 0.373 0.091 0.112 2012 383 171 0.322 0.275 0.105 0.101 XBH% = extra base hit percentage

He’s not being shifted much more recently, and his batting average on balls in play into the shift is not really a problem. Even his extra base hit numbers haven’t really been affected by the shift, not by in-play results at least.

So something else is going on, and we have to jump back into the smaller differences in his batted ball mix. It does look like he’s pulling the ball more on the ground. In terms of his spray charts, that cluster of line drives in the outfield have become ground balls to the shifted second baseman. (As an aside, that should tell you a little bit about how outcomes poison the line drive / ground ball distinction.) Watch the red down the line turn into green:

No matter what biases are in the stringer data, there’s a fact that he’s missing a cluster of 200-250 foot line drives, which are some of the best hits in baseball. That’s not good.

Maybe it’s age. 28 looks like it’s post-peak for power by any measure. Isolated slugging, batted ball distance, home runs per fly ball… they all peak before 28. It could just be age.

Still, it all seems so drastic. This is a four-win, 30-homer bat, and now he’s a replacement level 20-homer guy?

That knee injury looms large. Bruce himself told me “You come up out of your legs and create an around-the-ball plane rather than being able to stay connected to your back side and hit through the baseball to the big part of the field.” He also said “You try to create more with your upper body, which is more of a twist, and it’s up and out and around — that’s why I hit a million ground balls last year.”

The player said that going into this season. He claimed that he was healthy, and that he’d gotten healthy in 2014, but there’s healthy and there’s Healthy. You can see the catastrophic change in his ground-ball rate due to the injury. But it does look like the ground-ball rate got worse as 2015 went on, too. Watch the green line.

Bruce is a high ball hitter looking to drive the ball. He shouldn’t be hitting ground balls. And there’s no health update on his RotoWorld page, save for a note about his calf muscle in March. He was rested regularly, but never was it said that it was for a specific body part. Still, as the season went on, the ground balls went up, and the exit velocity went down:

Perhaps the league has run an adjustment on him and he hasn’t adjusted back yet. It looks like righties aren’t thrown inside to Bruce with their fastballs any more. Or, they’re burying it more in on his hands.

That probably hurts his ability to pull it in the air. He’s certainly not getting the same kind of pitches inside the zone when it comes to the fastball. And that’s the right strategy — despite a decent walk rate, Bruce has always reached at pitches outside the zone more than average. So pitchers have stretched him further inside and outside, and he’s rewarded them with ground balls.

To answer the titular question, it looks like age, injury, and approach have all combined to rob Bruce of his batted ball authority. One of those things he can improve with conditioning, the other isn’t likely to change 4600 plate appearances into his career, and the last is impossible to change for all humans. Bruce is up against it if he’d like to get his numbers back.