"They've got him so messed up running in circles he's forgotten what he was made to do... He's just gotta learn how to be a horse again."
Any scene with Pumpkin, the massive sweet-natured Clydesdale who goes everywhere with Seabiscuit, to keep him company.
It's small, it's subtle... but the one line, "I'd rather have you strong than thin." Half the reason Red lost almost all of his races, why he was so desperate and miserable and strung-out was because he'd been forced into an eating disorder to keep himself under 115 pounds, because all of his previous employers had held out his weight as a condition of letting him ride. And with that one line Charles Howard gives him permission to be a human being again.
When you realize Mr. Howard has grown to think of Red as a son, and is terrified of losing him like he lost his little boy.
"It's not just the leg—it's not! He could fall, he could get trampled! If he gets thrown from that horse...!"