Andrew McCutchen struggled early this season, but has turned things around drastically as of late.

As recently as last season, McCutchen's swing included a repeated motion involving his back foot. Right around the time of contact, his right foot would come up, drive forward and slam back down.

"McCutchen didn’t design his swing specifically concentrating on his back foot, but what this demonstrates is good and mostly complete weight transfer. Because of that weight transfer to the front leg, McCutchen’s foot leaves the ground," writes Jeff Sullivan.

Early this season, McCutchen was swinging without the same back foot motion. The foot wasn't really coming up, but lately he has started to replicate the motion we saw last season. 

The explanation may be the left knee pain McCutchen was dealing with. It may not have allowed him to fully transfer weight to his front leg, which kept his right foot on the ground.