SCOTTSDALE, Ariz. — A curveball to the helmet on Aug. 4 did more than end Brandon Belt’s season last summer. It did more than prevent him from setting a career high in home runs. It did more than deprive the Giants of their most productive left-handed hitter for the final eight weeks of a dismal year.



The Giants lost their first baseman for two months, but box scores couldn’t show the rest.



Haylee Belt lost a piece of her husband. Little 3-year-old Grayson lost a piece of his father.



That’s what it felt like at times, anyway.



“Small things would make me angry, and that’s not me,” Belt told The Athletic on Sunday. “And my family, they took the brunt of it. I’ve always tried my best not to take the game home with me. But that was something I couldn’t do anything about.”



Belt’s fourth documented concussion left him lethargic, frustrated and irritable. It dulled his playful,...