During Eyeshield 21's original run in the magazine, Inagaki went to the United States to see college football matches,[10] and National Football League games.[11] Despite having never played American football, Inagaki chose this theme after deciding that he wanted to create "a protagonist that was wimpy at the beginning, yet could perform outstandingly in a sports game", and with this premise in mind he decided that American football would be "a very suitable material."[9] When originally creating Eyeshield 21, Inagaki said he was wary because he did not want his manga becoming "a simulator of football".[12] The fact that football is not a popular sport in Japan also worried Inagaki.