Former Jacksonville Jaguars head coach Tom Coughlin was hired to replace Jim Fassel, who was fired following the conclusion of the 2003 season. Departures: Kerry Collins, Brian Mitchell, Kenny Holmes, Brandon Short, Cornelius Griffin, Keith Hamilton, Michael Barrow, Matt Bryant.
Due to their poor record from the previous season, the Giants were guaranteed one of the first four picks in the draft. Since they finished with the same record as the San Diego Chargers, the Oakland Raiders, and the Arizona Cardinals, tiebreakers would determine who received which pick and the Giants were given the fourth pick. That year, Ole Miss quarterback and Heisman trophy finalist Eli Manning was slated to be the #1 pick. That pick was in the possession of the Chargers, whom Manning was refusing to play for. Although forecasts saw the Giants picking either Robert Gallery, an offensive lineman from Iowa who went to the Raiders with the second pick, or Ben Roethlisberger, a quarterback from Miami of Ohio who went later in the draft to the Pittsburgh Steelers, the team was looking to trade with the Chargers to acquire the pick. Instead, on draft day, a scenario was initiated where the Chargers drafted Manning, the Giants drafted North Carolina State's quarterback Philip Rivers, and the picks were swapped for each other.
Although the Giants had traded for Eli Manning, the season began with veteran quarterback and former league MVP Kurt Warner as the starter. After a season-opening loss to the Philadelphia Eagles, Warner and the Giants enjoyed surprising success, starting a four-game winning streak that included road victories over the Dallas Cowboys and Green Bay Packers. Following a Halloween rout of the Minnesota Vikings, 34–14, the Giants were 5–2, trailing the then-undefeated Philadelphia Eagles by just two games.
The high-water mark of the Giants season came on November 7, when the Giants led the Chicago Bears 14–0 at the end of the first quarter. Over the rest of the game, though, the Giants turned the ball over five times, allowed the Bears to score 28 unanswered points (20 in the second quarter) and lost by a score of 28–21. After another loss, this time on the road against the Arizona Cardinals, Giants coach Tom Coughlin decided to replace Warner with Manning. The decision did not show immediate success, as the Giants turned the ball over ten times in the next four games, scoring a total of 37 points.
Close losses to the Pittsburgh Steelers and the Cincinnati Bengals followed, dropping the Giants to 5–10. The season did end with a glimmer of hope, however, as the Giants rallied from a 16–7 fourth quarter deficit to end the season with a 28–24 victory over the arch-rival Dallas Cowboys. Manning threw two fourth-quarter touchdown passes, and Tiki Barber scored the game winner.