What happened to Brett Gardner's bat?

Brett Gardner's spectacular skills at the plate helped make the Yankees the cream of the crop in the AL East during the season's first half.  They also garnered Gardner his first ever selection to the All Star Game.  Gardner certainly deserved it, as his 2.9 fWAR led the team, and his 139 wRC+ and .373 wOBA - coupled of course with his solid defense in the outfield - made him one of the better all-around players in the league.  While he might not have hit for as much power as Mark Teixeira or Alex Rodriguez, his ability to get on base and jump start the offense made the Yankees one of the most formidable groups in the majors at the dish.

However, since the break, Gardner has hit just .212/.318/.291 for a 74 wRC+.  While the Yankees have managed to continue to be one of the best offenses in the game, they desperately need Gardner to start hitting again if they want to keep pace with the Toronto Blue Jays.  While he was outperforming his career averages before, he certainly shouldn't have become this bad of a hitter all of a sudden.  So what has happened to Gardner?

One of the main causes of his drop off is the fact that he's hitting more fly balls in the second half than he did in the first.  Before the break, Gardner only hit flyballs 31.1% of the time - that number has jumped to 38.3% since the break, and it's corresponded with a 3% drop in his line drive rate.  Because he's not much of a power hitter, flyballs do not bring Gardner much success.  He's also not hitting the ball as hard recently, which has certainly not helped matters much.  Finally, Gardner's not making contact as much, and is striking out much more in the second half, which have both also contributed to his offensive decline over the last month and a half.

In particular, Gardner has struggled mainly against two pitches since the All Star Break: sliders and sinkers.  He's putting far fewer sliders in play and hitting fewer line drives on them since the break. Sinkers, however, have really proved Gardner's downfall recently.  Since he sees it more than any other pitch but four-seamers, his lack of production on this pitch has hurt him quite a bit.  Against sinkers, he's hitting both more grounders and pop-ups in the second half (but once again, far fewer line drives), he's whiffing far more on them, and to make matters even worse, he's swinging at more sinkers now than he was earlier in the year.  Simply put, he's trying harder to hit sinkers, but he's making worse and worse contact against them.  Since it's a pitch he sees so often, his inability to make solid contact with them and drive them out of the infield has been a major part of his struggles.

Finally, Gardner seems to have altered his approach at the plate a bit in the second half.  Take a look at his swing profile from the first half of the season:

In general, he's got a great eye, and this stretch shows it - he typically only swung at pitches in the middle of the zone.  Now, here's his zone profile from recent games:

Nothing major has changed, but what jumps out is the fact that he's swinging less at pitches down the heart of the plate, and swinging more at pitches on the edges of the strike zone, specifically up and away and down in the zone (especially down and in).  This has contributed to increased pop ups and ground balls, and to his general lack of good contact in the second half this year.

While some of Gardner's struggles are just the ups and downs of a long baseball season - and a good player cooling off a bit after a terrific first half - his weak contact, his struggles against sinkers, and his changes in his approach have not done Gardner any favors.  If he can get back to hitting line drives to all fields and stop swinging as much at pitches down in the zone (which with a swing like his are more likely to become grounders), Gardner should be able to bounce back.  Hopefully, for the Yankees sake, he makes the adjustments he needs to and gives them more punch at the top of their lineup.  With the Blue Jays - who sport the best offense in the majors - ahead of them, the Yankees are going to need it.