The Philadelphia Phillies slugger used a blue bat in his first plate appearance against San Francisco as part of a gender reveal for his fourth child.

That's because with a baby blue bat, Harper revealed to the fans in the stadium -- and all around the world -- that the baby he is expecting with his wife, Kayla, will be a boy. They're having a boy!

The Philadelphia Phillies slugger used a blue bat in his first plate appearance of Monday night's game against San Francisco as part of a gender reveal for his fourth child. A two-time NL MVP, Harper ...