Factual error: During Gavin Grey's first NFL game in 1957, the helmets depicted for both the Washington Redskins and Pittsburgh Steelers are historically inaccurate. The Redskins did not employ the burgundy helmets with the feather-stripe running along the center until 1958, and the Steelers didn't use black helmets with the Steelmark logo until 1963. In 1957, the Redskins used solid gold helmets while the Steelers used yellow helmets with a black stripe along the center and black numerals on either side.
Factual error: In the scene where Gavin makes his comeback with the Denver Broncos, one of his opponents is the Pittsburgh Steelers. Gavin was inspired to join the AFL's Broncos after watching the Jets victory in Super Bowl 3. That Super Bowl was for the 1968 season so its safe to say Gavin's comeback with Denver was in the 1969 season. The AFL and NFL didn't merge until the 1970 season and in 1969 the Steelers were part of the NFL. Therefore, there is no way the Broncos and Steelers would have played each other during the season of Gavin's comeback.
Factual error: During the scene of Gavin Grey's final NFL game with the Denver Broncos (the snowy night game against the Patriots), the footage of Gavin watching helplessly from the sideline is mixed with actual footage from a 1978 meeting between the Broncos and Patriots - former NFL players like Steve Grogan, Rick Upchurch and Steve Foley are noticeable in the game footage. Given that he was an NFL rookie in 1957, this would make Gavin Grey over 40 years old during his final game. It is highly unlikely that any NFL team would employ a 40-year-old as a starting running back. It also implies that Gavin Grey's brief comeback attempt lasted nearly ten seasons, which is also highly unlikely.