When Tommy and Brendan first meet and talk before the tournament, Tommy resents Brendan for staying by his father, Paddy, when Tommy and their mother ran away. Brendan states in defense, "I was a 16-year-old kid." This would make Tommy 14 years old when he left with his mom - which would make it impossible for him to be a high school state champion wrestler under the training of Paddy, as is mentioned in the beginning of the film.
North Hills Senior High School, where Brendan taught physics, and the Twin Highway Drive-in theater, where his students watched the final two fights, take place in Philadelphia but are actually located in Pittsburgh, where most of the rest of the movie is set.
When Paddy tells Tommy that he'll leave the coffee out until 0500 hours (5:00am), a digital alarm clock in the background reveals that the time is already 5:23am. Tommy was speaking in reference to future wake up calls from his father and his father, speaking in the future, said the coffee would stay on until 0500.
(Flopped shot) During the final bout, Tommy looks over at the crowd of U.S. Marines. All of their ribbons are mounted over their left side. when shown again they are on the right side and in the last shot there on the left side again.