Jerry's feelings after being tackled on the football field in the first chapter pretty much sum up how he feels about the world in general at the beginning of the book - "he had never felt so lonely in his life, abandoned, defenseless".  His mother, whom he loved very much, has recently died after a long and painful illness, his relationship with his father is strained, and he is a freshman at a new school, desperately trying to find a place for himself.  He's also "got guts", as he shows in his fierce determination to make the football team against all odds.