Fantastic Leg Kicks and Where to Find Them

Thousands of hitters dig into a professional batter’s box every season and all of them, despite sharing a common goal, do their jobs in a way that is individually exclusive. The moments between when a hitter decides to swing and when he impacts the baseball – or doesn’t – are filled with countless, hitter-specific traits that comprise a baseball swing. Bat speed, load depth, load height, lever length, head movement, stride length, stride timing; the list of the bio-mechanical variables is comically long. These swings, and the constant adjustments hitters are making to them are the snowflakes of summer. They are wholly unique works of art, tirelessly crafted until some advance scout or opposing catcher sees a hole, exploits it, and forces the hitter to patch and rebuild.

A recent pervasive and effective swing adjustment which has aided some of the most notable leaps in performance among Major Leaguers is The Leg Kick. An increasingly popular style of hitting footwork, the leg kick (that’s what we’re calling it in this piece, anyway) occurs when the hitter lifts his front leg high off the ground and draws his knee up toward his body before taking a big, aggressive stride back toward the baseball during the swing.

This has a few functions. First, it allows the hitter to utilize their lower half in an athletic way by loading all their weight onto their back foot before that potential energy becomes kinetic and explodes back into the ball. Simpler, more conservative strides simply don’t add as much to a swing. It also, as some hitters have described, aids with a hitter’s timing as certain aspects of the swing get set earlier – often before the pitch is even thrown – which gives the hitter less to do later in the process.

Some of the hitters who have integrated an aggressive leg kick into their swing have become monstrous offensive contributors of late. Most notable of these is Josh Donaldson whose early big league swing featured a little toe tap before it evolved into the MVP caliber cut we know today. 

Then Athletics hitting coach Chili Davis -- who has played a role in a number of late-blooming hitters' careers -- had the following to say in a Jon Morosi piece on Donaldson's life:

"His swing, when it’s under control, is a power swing. He generates a lot of power through his body. And when he’s making good contact, he can do damage to a team in a lot of ways. Now, that swing would be pretty hard to teach because of all the movement in it — the leg kick, the hands dropping and coming back up. But the key to that swing, and that approach, is being under control — being slow and early with the leg kick, not stompy or jumpy. Being under control with your mindset, not trying to force the issue. Get a pitch I can hit and square it up. And trust that, if I square it up and get through it, I’ve done all I can do and something good can happen."

Note how often Davis mentions the need to be "under control" and stash that in the back of your mind because we're coming back to that later. 

Donaldson, at his kick's pinnacle. From the Morosi piece.

Here's what Donaldson said about the change:

I’ve watched unlimited hours of Jose Bautista on film. What led me to leg kicking was him. I was always in between — doing a leg kick, toe tap, getting my foot down. When I saw that, I said, “I feel like I can do that every day.” So I’ve stuck to it.

Yes, Jose Bautista (old, new) is another of many hitters who have benefited from the change. Marlon Byrd (old, new, in-depth) Justin Turner (old, new) and the suddenly healthy and elite A.J. Pollock (old, new) have all made similar modifications that have coincided with dramatic statistical improvements.

Justin Turner

Perhaps the most successful implementation of the leg kick came more than 50 years ago when Yomiyuri Giants 1B Sadaharu Oh, after converting to hitting full time, adopted his famed “flamingo” leg kick.  As outlined in his auto-biography, The Zen Way of Baseball, Oh was craving something to aid with his timing and, with consultation from hitting coach Hiroshi Arakawa, developed the kick which helped turn Oh into one of the greatest hitters ever to walk the earth.  

Lest ye believe this sort of mechanical adjustment is some sort of magical slugging elixir that would benefit any hitter who might adopt it, the leg kick is a double-edged sword. Such a boisterous mechanical feature can be difficult to control and it can create issues with balance, posture and embarrassingly early weight transfers that result in the world’s ugliest swings. Oh also notes these concerns in his book and describes his own tireless practice sessions which included repeatedly swinging in front of a mirror. With a samurai sword. All to train himself to avoid the leg kick’s many potential pitfalls.

Cubs infielder Javier Baez has struggled to tame his own leg kick and is in the midst of mechanical adjustments to tone things down. Baez has some of the most electric bat speed scouts have ever seen from any hitter, let alone a middle-infielder, and elite raw power but his 2014 debut was mired by strikeouts. A .169/.227/.324 line and 41% strikeout rate won’t cut it, even at a 30 home run pace and evaluators league-wide were concerned that Baez’s problems went far beyond the usual struggles newly risen prospects often endure. 

Baez began his season rehabbing in the rookie-level Arizona League and was clearly trying to dilute things. I attended some of his rehab appearances and, as you can see in the video below, Baez has been working to either situationally or completely eradicate his big stride and try to find a happy medium between his natural power and his ability to tap into it. Early returns have been positive as Baez has a .798 OPS in 53 Major League plate appearances this year.

Pederson's ground balls per BaseballSavant.com

Another young hitter who might benefit from by reexamining his own extreme stride is Dodgers CF Joc Pederson. His leg kick is so violent and aggressive that he often has difficulty maintaining his posture and will begin falling down the first base line mid-swing. This has resulted in lots of groundballs to the right side of the infield, enough that opponents are now shifting Pederson and suppressing his BABIP down to a career-standard .275 after it was hovering over .300 in April and May. This corruption of Pederson’s posture has also made him vulnerable on the plate’s outer half and pitchers have taken notice. According to BaseballSavant.com, twenty-five percent of the pitches Pederson has seen this year have been down and away out of the strike zone where Pederson can’t do damage. It seems to be working. Pederson has seen his average exit velocities dip as the season has gone on. They’ve been below league average seven of the last nine weeks.

2015 pitches to Joc Pederson, from catcher's perspective. (Via BaseballSavant.com)

Yes, Pederson has had a tremendously productive rookie season as a three-true-outcomes hitter who plays an up the middle position. He’s been worth nearly 3 Wins Above Replacement. But he’s been trending in the wrong direction since July and is going to have react to the adjustments the league has made to him to repeat that level of value next year. Perhaps simplified footwork would be beneficial, though it’s difficult to imagine Pederson undergoing a mechanical overhaul in the middle of a pennant race. Dodger's Digest writer Chad Moriyama posited that Pederson actually embellished his leg kick coming into the season. As I saw last weekend when the Dodgers were in Arizona, it generates mixed results.