For Panthers coach Ron Rivera, it wasn’t enough that his team lost a heartbreaker in Atlanta to their NFC South rivals. The manner in which they lost is the most frustrating part.

Rivera is a defensive man to his core. As a player, he spent nine years at linebacker for the Chicago Bears and was a part of the storied 1985 Super Bowl team. As a coach, his stops in Philadelphia and San Diego consisted of roles of defensive coordinator and linebackers coach.

In Charlotte, Rivera always emphasized having a strong core on defense. His units are usually among the NFL’s best.

Against the Falcons, however, the Panthers’ rush defense was horrid, allowing 170 yards on the ground. The defense also racked up seven penalties for 49 yards. After the game, Rivera was adamant about his disapproval, and he vowed that a performance like this won’t be tolerated on his watch, via Nick Carboni at WCNC.

Ron Rivera calls #Panthers run defense "terrible" and "undisciplined." "To be a defensive head coach and have that happen, I won't stand for that." — Nick Carboni (@NickCarboniWCNC) September 16, 2018

Tevin Coleman was the worst problem for the Panthers. He ran for 107 rushing yards, the first time Carolina has allowed a 100-yard rusher in 22 games.