Although it officially dates back to November 1970, the rivalry between the Cincinnati Bengals and Pittsburgh Steelers took a few explosive turns in 2015, contributing to perhaps the most hate-filled series in professional football.
If there was any doubt about the hatred these teams had for each other, that doubt faded after three intense meetings.
Penalties, pregame scuffles, postgame tweets and a playoff meeting defined the games between the longtime foes.
With both teams' seasons now over, we look back at four ways their rivalry affected the 2015 season:
More key late-season injuries. For the past two seasons, injuries that came in the teams' final meeting might have led to earlier-than-expected endings to their seasons. Just last week in the wild-card-round playoff meeting in Cincinnati, a hit from Bengals linebacker Vontaze Burfict to Steelers receiver Antonio Brown's head gave Brown a concussion that he couldn't recover from in time to appear in Sunday's divisional-round loss at Denver. Bengals tight end Tyler Eifert had his own head injury during his team's playoff chase that forced him to miss two of Cincinnati's last three regular-season games. His concussion came after a helmet-to-helmet blow by Steelers safety Mike Mitchell in the December game. In last year's regular-season finale at Pittsburgh, Steelers running back Le'Veon Bell also was lost for the year after a hard hit to his knee from Bengals safety Reggie Nelson. Pittsburgh lost its wild-card game the next week. In that same finale, Bengals receiver A.J. Green left with a concussion after another hit from Mitchell. Green, too, was unable to play in Cincinnati's wild-card-round game a week later.
Refs keeping an eye on coaches. Officials could start monitoring the sideline a little closer in future seasons after assistant coaches were involved in pivotal plays in the Steelers-Bengals playoff game. It already appears that discussions into this matter have taken place. During last week's game, Steelers offensive line coach Mike Munchak grabbed Nelson's hair as the dreadlocked defender entered Pittsburgh's sideline at the end of a play. Steelers linebackers coach Joey Porter also was on the field during an injury timeout, causing an angered Adam Jones to draw a penalty after the Bengals corner made contact with an official while reaching for the coach. Both coaches were later fined $10,000.
Discipline an issue? Based on his team's performance in the wild-card game, there were questions raised about whether Bengals coach Marvin Lewis had lost control of his players. As many Bengals contended, all week before the game, Lewis' message harped on them keeping their poise. They knew Porter might try to get a rise out of them, and they knew the Steelers would want to get them to retaliate after the whistle. For the most part, the Bengals stayed cool, but at a pivotal time in the fourth quarter, they received a pair of penalties that played a role in their fifth straight first-round exit.
Jones could be gone. Jones, who had a costly late-game penalty, could find himself a casualty because of his lack of poise. As great as he played for the Bengals in 2015, two penalties -- the one involving Porter, and another that involved him pulling off Raiders receiver Amari Cooper's helmet in the season opener -- could be enough for the Bengals to let him hit free agency without offering a new deal. The 2016 Steelers-Bengals games would have a dramatically different feel if he wasn't part of the rivalry. This past regular season, he and fellow corner Dre Kirkpatrick held Brown to just 47 and 87 yards receiving in the regular season.