Ask Aaron Boone what has gotten into Giancarlo Stanton lately, and the Yankees manager will tell you that the 35-year-old has “mastered” the mental side of baseball.

Such was the case on Tuesday before the Yankees hosted the Nationals.

“He knows how to get himself ready,” Boone explained. “He knows how to prepare for a pitcher. He knows how to play the game within the game, that cat and mouse thing with the pitcher, really good.”

Boone delivered those comments hours before Stanton powered the Yankees’ 5-1 win over the Nationals, as he first emptied loaded bases with a 101.6-mph double off MacKenzie Gore in the third inning. A 112.7-mph, two-run homer off Orlando Ribalta followed in the sixth, giving Stanton a season-high five RBI.

The explosive evening continued what has been a sens

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