Although the Falcons' offense struggled, the defense was dominant. The Falcons' 129 points allowed not only led the league, but established an all-time NFL record for fewest points allowed in a 14-game NFL season. Atlanta's 3,242 total yards allowed were second-fewest in the league, and the Falcons' 1,384 passing yards allowed was by far the best in the NFL in 1977.
Football analytics site Cold Hard Football Facts call the 1977 Falcons "the stingiest defense of the Super Bowl Era. In fact, it was the stingiest defense since World War II. Atlanta surrendered just 9.2 PPG, or a total of 129 points in the 14-game season. For a little perspective: the 2012 Bills gave up 131 points in their first four games. That unit was truly a no-name defense at its finest: despite its status as the stingiest defense since World War II, the 1977 Falcons sent only two defenders to the Pro Bowl: cornerback Rolland Lawrence and defensive end Claude Humphrey. [...] It was truly a one-hit wonder of a unit: the 1976 Falcons possessed one of the worst defenses in the league (22.3 PPG); and it largely fell apart in 1978 (18.1 PPG). The most famous personality on the 1977 Falcons was not a player but defensive assistant Jerry Glanville, who installed in a swarming style of play in Atlanta remembered as the "Grits Blitz" defense."