Continuity mistake: In the first of Red's boxing fights he gets very badly hit on his right eye. When he is leaning against the ropes blood is running down his cheek, but when he turns around the lower part of his cheek is clean. (00:25:25)
Continuity mistake: In the movie, War Admiral is described as standing 18 hands tall, compared to Seabiscuit's 15.2 hands. Although this is not historically correct (according to contemporary sources, both horses stood around 15.2 hands) the size disparity created by the movie is not carried on in the match race, where the two horses appear to be the same size.
Continuity mistake: Before the race at Pimlico a crowd of reporters is waiting at the stable window for Seabiscuit to be worked out. The way they are leaning in the window sill varies greatly between close-up and a wide angle that shows them and Tom. (01:26:50)
Factual error: The doctors tell Red he has broken his leg in 13 places, however the X-ray shown later is not indicative of an injury of that nature. The two fractures you see in the X-rays are considered non-unions (fractures that aren't healed properly and are unstable) but we should also see some type of hardware that would be needed for that many fractures. Surgeons have been using internal screws on fractures since the turn of the century.
Continuity mistake: When Charles gives Red $20 with his left hand he is holding a newspaper under his right arm. The camera angle changes that we see Charles' upper body from behind, he puts his right hand on Red's shoulder, and when we see the whole Charles again the newspaper has disappeared. (01:04:00)
Continuity mistake: When all the protagonists are sitting on one bench in church Red has a big smile on his face. When the camera angle changes to a close-up his smile is completely gone. (00:55:10)
Continuity mistake: After the death of his son we see Charles sitting in an armchair playing with the small marble game. The way he is holding the game changes back and forth between shots. (00:22:50)
Continuity mistake: After the car race into the mountains Charles gives a speech. When a photographer takes a picture a huge cloud arises from the flashlight and drifts over to Charles. However, in the next two shots the cloud is gone, but in the third shot it's back again. (00:07:55)
Revealing mistake: After the race where Seabiscuit beats War Admiral, we see the train on the return trip home. If you look closely, the engine number on the locomotive is reversed, indicating that the film was flipped.
Other mistake: Red Pollard's operation for his injured leg occurs over many hours (as evidenced by the changing light and darkness on Tom Smith as he waits for the results.) Yet when the doctor appears to tell Smith that Pollard will walk again, he seems to be freshly shaven. Surely if he had just been involved in a lengthy surgical procedure, he would not have had time to shave.
Plot hole: Immediately after Seabiscuit injures his leg, the track vet tells owner Charles Howard that the horse will never race again. He offers to euthanize Seabiscuit, even though it was not a life-threatening injury. Even if Seabiscuit was unable to race again, a champion racehorse has more value as a stud horse. It is nearly inconceivable that a random vet would suggest this so early on. If anything, it would be "wait and see."
Continuity mistake: Before his first race after his accident Red puts a leather brace on the injured leg. He ties it in front, but when he walks over to Seabiscuit the brace is tied on the side. (01:59:20)
Continuity mistake: When the protagonists listen to Mr. Riddle on the radio Tom's hand covers his mouth. When the camera angle changes he is holding his arm over his stomach. (01:12:45)
Factual error: When Charles gives Red a $20 advance he hands over a modern bill. (01:03:40)
Continuity mistake: When Red is telling the new jockey all about Seabiscuit's peculiarities, he tells the jockey not to use the crop on the left because a previous trainer had beaten him on that side. Earlierwhen the horse was working with that trainer, they show him being beaten on the right side.
Continuity mistake: Before the match race between Seabiscuit and War Admiral, Charles and Mr. Riddle take their seats. They exchange a few words, then Riddle turns away to talk to his seat neighbor, but when the camera cuts to Charles we see Riddle in the background still looking at him as he did before. (01:37:20)
Continuity mistake: When Chris Cooper is standing next to the barbed wire fence at the beginning of the film and he puts his finger on it, the positioning of his hand is different from the wide shot to the close up. (00:07:25)
Answer: Red asked for $10 because he needed to see a dentist, and Howard gave him $20.