Vincent wrote letters to the team and Brady saying a league-sponsored investigative report established "substantial and credible evidence" that the quarterback knew the employees were deflating footballs and failed to cooperate with investigators.

The investigation by attorney Ted Wells found that Brady "was at least generally aware" of plans by two Patriots employees to prepare the balls to his liking, below the league-mandated minimum of 12.5 pounds per square inch.

The Patriots defeated the Indianapolis Colts 45-7 and went on to beat the Seattle Seahawks in the Super Bowl.

The fine matches the largest the NFL has handed out, to Ed DeBartolo Jr., then the San Francisco 49ers' owner, who pleaded guilty to a felony in his role in a Louisiana gambling scandal in 1999.

Vincent told the Patriots the punishment was handed out regardless of whether the flatter footballs - which can be easier to grip and catch - affected the outcome of the blowout win over the Colts. Vincent said the flattening of balls probably began much earlier.

"While we cannot be certain when the activity began, the evidence suggests that January 18th was not the first and only occasion when this occurred, particularly in light of the evidence referring to deflation of footballs going back to before the beginning of the 2014 season," he wrote.

"It is impossible to determine whether this activity had an effect on the outcome of games or what that effect was."

It's the second time in eight years the Patriots have been punished for violating league rules. In 2007, the team was fined $500,000 and docked a first-round draft pick, and coach Bill Belichick was fined $250,000 for videotaping opposing coaches as a way to decipher their play signals.