The Miami Sharks, a once-great American football team, are now in turmoil and struggling to make the AFFA (Associated Football Franchises of America) playoffs in the year of 2001. They are coached by Tony D'Amato who is a thirty year veteran.
During the first game shown, which is the thirteenth game of the season, both the starting quarterback Jack "Cap" Rooney (Dennis Quaid) and the second-string quarterback Tyler Cherubini are injured and forced to leave the game due to poor offensive line play in blitz pickup. (This leads to a recurring theme that "on any given Sunday, anything can happen.") The ailing and increasingly desperate Sharks are forced to call upon third-string quarterback and former seventh-round draft pick Willie Beamen (Jamie Foxx). Beamen is visibly nervous and makes a number of errors illustrating his lack of knowledge regarding the team's playbook. During one play he lines up under the guard instead of the center, and he later in the game he audibles to a play which does not exist. He throws up in the huddle, which begins a ritual that he follows every game, reminiscent of Hall of Fame Buffalo Bills quarterback Jim Kelly. While the Sharks lose this game by a small margin, Beamen plays well and gains confidence.
During the next game Beamen begins to get comfortable with the game and quickly learns the offense. However, he dislikes the Sharks' conservative offense and much to the dismay of both Coach Tony D'Amato (Al Pacino). Beaman begins to change the plays in the huddle, not realizing the disrespect this shows to his coaches. Beamen displays his raw athletic talent and starts to run and pass extremely successfully and leads the sharks to the playoffs after winning the last three of the last four games of the season, bringing the Sharks to 9-7 on the year. Beaman's new found success results in a growing narcissism and arrogance. He becomes "Steamin'" Willie Beamen, the new poster boy for the AFFA, and receives numerous lucrative advertisement deals, including a music video.
His new-found success, and inability to handle it, leads to tension within the Sharks locker room and the front office. D'Amato confronts Beamen to ask why he has been changing the plays, to which Beaman responds selfishly. After displaying to D'Amato that Beamen is not capable of leading the team, D'Amato tells Beamen that it is likely that 'Cap' Rooney will probably be fit and available for the playoffs, demoting Beamen back to the bench. Beaman fails to understand the team concept as he is filled with self-pity about how his career has been until he got a chance to play.
A rift forms between Beaman and D'Amato after D'Amato tells him just how far he still has to go to fulfill his potential and lead the team. After learning of his demotion he alienates the rest of the team, to the point that he gets his car sawed in half at a party, and the Sharks are blown out at home in a game that could have given the Sharks home field advantage in the playoffs. Beaman contemplates and amends his selfish behavior.
In the final game, Miami manages a come-from-behind win in the final seconds against the Dallas Knights, winning the first round of the playoffs. The final game sees Cap return to start as quarterback and he plays strongly until being injured by a hit. His replacement, Beaman, apologizes for his actions to the team in the huddle on the game-winning drive. Off-screen, Miami beats Minnesota for their conference championship and then loses to San Francisco in the Pantheon Cup Championship 32-13 (reminiscent of Super Bowl XIX).
At D'Amato's final press conference as head coach, all feuds have been resolved or at least put on hold and he leaves on a positive note, being thanked by owner Christina Pagniacci (Cameron Diaz) and the media for his contributions to the team. D'Amato is then expected to announce his retirement, but then drops a bombshell and announces that he has been hired as Head Coach and General Manager of the expansion team Albuquerque Aztecs. He adds that he signed Willie Beamen as his starting quarterback and franchise player, after the Sharks refused to extend Beamen's expiring contract mid-season. As the scene ends, Christina and the other executives are angrily asking Crozier how he could have let Beamen finish the season without re-signing him to a longer contract for the Sharks.
Despite the initial hysteria among the media and owners, the general consensus is that this is the best solution because D'Amato and Crozier (backed by Christina) cannot co-exist. This would also possibly allow Cap Rooney to remain Miami's starting quarterback for the next season and retire on his own terms, instead of risking being demoted to backup.