Crop out the slump.
Despite what you may have heard, Bruce as a .850 OPS/.360 wOBA/very good player is not somehow worse than a player with the same stat line who might arrive there with less streaky production - unless you can show that Bruce only contributes in games the Reds' would have won or lost by a wide margin.
It should also be mentioned that, despite his recent struggles, Jay has a .366 wOBA (higher than he's posted in any single season previously).
His fits and starts do prompt the question as to what's driving him to look so lost after recently looking so terrific and almost the best.
On May 8, Jay was hitting a svelte .306/.342/.667. That wasn't even 3 weeks a go, so please tell me I'm not wasting my time on this post. I'm already 4 internet paragraphs in, so there's no turning back. Since then, he's been tumbling. Over the last two weeks, he's been the Reds' worst regular, hitting .163/.255/.256. His OPS is .214 (!) over the last 7 days.
During that time, he has a 35.3% K-rate and the lowest line drive rate of any non-Rolen/non-pitcher
Why? Is this stretch pure noise in the context of an 162 game season or is it something deeper, possibly endemic to his previous slumps? Good question. I guess. Honestly, I wonder if it's not just the fact that it's only been like 2 weeks. Two, two and a half...
I'd be happy with the small sample size explanation if the slump wasn't so deep or part of a pattern. After the jump, a few recurring factors that might help explain.
This is impossible to test, but given that Bruce is nearing his 2,250th major league PA, his boom and bust tendencies are pretty established. He might simply be the kind of player whose struggles create a negative feedback loop that's hard to get out of it - and vice versa for his productive periods.
It doesn't help that he's gotten railroaded on a few calls, which has alsol served to make his frustration more evident.
Quality of competition
Over the past 15 games, with the exception of 3 games against the Brewers, the Reds have played teams with winning records. Milwaukee, for its part, threw Greinke in that series - a pitcher Bruce hasn't hit at all so far in his career. The schedule hasn't been easy and, along with the rigors of road-tripping (and 20 games in 20 days), may create an especially hostile environment for Bruce to get out of a slump.
In 4 of 5 games in which Bruce failed to reach base (over the last 2 weeks), he faced good pitchers he had struggled to hit in the past: Zimmerman, Dickey, Beachy and Hanson. In the fifth, it was Andy Pettite, who none of the Reds could touch.
Despite bringing his platoon splits into much better line last season, Bruce is struggling with lefties again this season. But it's only been 50 plate appearances to date. As his splits early in his career suggest, Bruce can sometimes struggle to read pithces coming across his body. He may simply have to get further into the season to get his timing back.
Historically, Bruce has had his struggles with off-speed stuff, though he's improved in his ability to lay off the "low and away" (pick up The Low and Away's album, The Theory Experiment, on Tragis Records). In his current slump, he's whiffing almost once every four curveballs - which says to me he's both not seeing it well and facing some pitchers who know how to throw a bendy one. He's also missing four seamers a lot more than usual, suggesting he's eager and overcompensating.
He's also seeing more sliders recently and fouling more of them off, but still retaining the discipline he's shown so far this season (less swings out of the zone).
It's all a noisy mess at this point, but I suspect he's getting frustrated most by curveballs, which is bleeding over to cause him to make worse swings on other pitches. When he isn't whiffing, he's getting strikes hung on him by fouling more pitches off.
Related is the fact that while Bruce is chasing less and pitchers are pitching him out of the zone more, he's seeing more first-pitch strikes than ever. He may have to adjust to the fact that pitchers are coming after him more down and away or down and in. A slump can create a multiplier effect: taking more first pitch strikes, more foul balls and turning them into a lot more pitcher-friendly counts.
Fly ball luck
Over his slump, Bruce isn't hitting the ball very hard when he does make contact, but he is hitting a lot of fly balls. As in the case of his foul balls, he might be "just missing" and suffering a little bit of batted ball luck. His fly ball rate is higher than any position player other than Ludwick over the last two weeks, but his HR rate is 0%.