Bryce Harper says he knows one reason balls were flying again at the Home Run Derby: The baseballs are juiced.

He declined to say how he knows this but sounded certain off a derby that saw him launch a ball 482 feet.

“I’m not going to answer that. But they’re juiced,” Harper told The Post. “Everybody knows it. They do it every year.”

The Derby is an exhibition, so it wouldn’t be crazy or unfair to juice them, and even Harper himself (and Mike Trout) have advocated for metal bats to be used in the Derby.