Two days after his team was knocked out of the wild-card round of last season's playoffs, Cincinnati Bengals coach Marvin Lewis made a sobering admission.
He hadn't initially taken seriously some troubling concerns his players had raised in the middle of the season about teammates' off-the-field activities: His players had been trading threatening tweets with members of the Pittsburgh Steelers after Cincinnati's rivalry win in November.
Some of the most vicious rhetoric targeted Bengals linebacker Vontaze Burfict, the man who has spent the past four seasons as Public Enemy No. 1 in the Steel City. Burfict did himself no favors when, during the Bengals' Week 8 victory, he celebrated a tackle of Steelers running back Le'Veon Bell, who suffered a season-ending knee injury on the play. It was the second straight season cut short for Bell because of a hit from a Bengal.
"Unfortunately, the social media stuff let things get out of hand," Lewis said in January, referencing the series of tweets from two months prior. "I was negligent in not understanding all of that until it was too late. I apologized to our players for that after the first time around. I didn't realize it was going on like that. I thought it was chatter, no big deal. But some people think it's more significant than others."
Just when it seemed the rivalry between the Bengals and Steelers couldn't get more intense, it did.
Although the rivalry officially dates to November 1970, some of its ugliest moments have occurred in the past 10 years.
Aside from the social-media showdown, here are some of the most explosive on-the-field incidents in recent Bengals-Steelers history:
January 2006: Bengal-turned-Steeler Kimo von Oelhoffen grabbed Cincinnati quarterback Carson Palmer's left leg and then rolled into it. Palmer tore his ACL less than five minutes into the wild-card playoff game. In the playoffs for the first time since the 1990 season, the Bengals had high hopes for that postseason.
December 2014: Former Bengals safety Reggie Nelson drove his helmet into Bell's knee on a low tackle that caused Bell to miss the playoffs, which began a week later. In that same game, Bengals receiver A.J. Green was also injured by a hit from Pittsburgh safety Mike Mitchell; Green sustained a concussion and missed the playoffs.
November 2015: As Burfict tackled Bell from behind, the back's leg got caught awkwardly. Immediately after the hit that ended Bell's season, Burfict ran across the field and demonstratively celebrated the stop.
January 2016: A series of hard hits on both sides, two incidents involving Steelers assistants, constant chatter between players, more concussion-inducing hits, a pair of late Bengals penalties and a costly Bengals turnover all contributed to one of the wildest playoff games in recent NFL history.
It's hard to pinpoint exactly what's made this rivalry so intense lately. Maybe it's simply the Bengals' recent regular-season success, which means so much more is at stake for these AFC North teams. Whatever the source of the intensity, this rivalry is certainly among the league's most riveting.