Garber, the Nationals infield coordinator, began working with Zimmerman during his recent rehab stint in the Nationals’ minor league system. Zimmerman felt prolonged stiffness and soreness in his surgically repaired abdominal muscle while making throws, and he approached Garber about changes he wanted to make. “It’s slowly evolved from that,” Garber said.

This afternoon, Garber watched as Zimmerman fielded a ball and cro-hopped into a position unfamiliar to those who have watched Zimmerman throw. The pronounced extension of his right arm was gone, replaced by a 90-degree bend in his elbow. Zimmerman was more crouched and upright rather than bending backwards.

Zimmerman made the changes, which Garber is still working with him on, in order to both improve his throwing and to guard against a future injury to his midsection. Garber is uncertain as to whether his old motion led to Zimmerman’s injury, but he thinks changing it will help eliminate future injury.

“It’s just trying to make him more efficient to protect his body, so that he’s efficient as he could be so he doesn’t hurt that area,” Garber said. “As he was coming back, he had some stiffness and soreness there. Not wanting to get into bad habits, we’re just trying to get it where he’s efficient as he can be. We’re just trying to get it protected in that area.”

The clearest change is the “arm stroke” Zimmerman uses to throw. Garber and Zimmerman made it shorter, which allows his core and his legs to provide more power. With his old, straight arm swing, Zimmerman relied too much on his arm strength to throw, and enough on transferring power from his lower body into the throw.

The Nationals and Garber are “making sure that his body, that the core mechanics work together, and they’re smooth,” Garber said. “He’s incorporating his legs, he’s in good position, so that it’s a nice, smooth path to the throw. He’s working on getting into a good position to throw, and then getting used to getting his legs into his throw, to make sure that arm works as clean as it can work to protect his body.”