He had just been flagged for roughing the passer on Indianapolis Colts quarterback Andrew Luck, or more specifically, using his full body weight to try to get the sack. Not only did it give the Colts a first down on a key third-and-7 play, but it was the second time Dunlap had been flagged for roughing the passer in a game.
He was fuming -- and not afraid to show it.
Two plays later, Dunlap came off the edge and pulled Luck down, making sure he didn't land on him this time. Dunlap had the sack he thought he deserved, and the Bengals had all the momentum on their side on the way to a 34-23 victory.
"I was upset," Dunlap said. "I mean, I tried to do the next best thing and keep all my weight from taking him to the ground. I planked and rolled off right away, and I tried to let the referee know that I'm not trying to be malicious and drive him into the ground, because I know it's Andrew Luck after two years, so they're going to call it tight regardless."
It's possible that Dunlap's fury sparked the Bengals to a comeback. Perhaps it made his teammates a little angry too. Running back Joe Mixon ripped off a 13-yard run on the first play of the Bengals' next offensive series and got 49 of his 149 total all-purpose yards afterward.
As to what transpired on the sideline in between, Dunlap wouldn't say. But his grin said it all.
"That's my guy," Dunlap said of Mixon. "We're going to keep that between us, but we feed off each other."
Of course, quite a few other things had to happen for the Bengals to turn a 23-17 deficit into a 34-23 win. First, the Colts missed a 55-yard field goal. Then they committed three defensive penalties on the next series to help get the Bengals back into the end zone.
The Bengals tacked on another field goal and sealed the game with an 83-yard fumble return by safety Clayton Fejedelem, who wouldn't have even been in that position had Shawn Williams not gotten ejected early in the game.
"Maybe I was just due for one then," Fejedelem said.
Fejedelem said the Bengals were bracing for the possibility of multiple penalties against Luck, who is one of the faces of the league despite not having played a game since 2016 due to injury.
"Andrew Luck is a great, great quarterback coming off two years of not playing," Fejedelem said. "We knew they were going to protect him. He's a tough guy and the refs were going to -- it's hard when the game is put in the ref's hands a little bit.
"It's questionable, but it's a quarterback-driven league. They're going to protect the quarterback."
But for Dunlap and the rest of the players, the biggest thing was shaking off those moments and moving on to the next play.
"You don't get time to hiccup or flinch," Bengals coach Marvin Lewis said. "You've just got to keep playing, the game's on. Andrew Luck, as I told him after the game, ‘You're back.' Because he was throwing that ball today."
The Bengals know they didn't play well for much of the game -- from an early interception thrown by Andy Dalton to two fumbles by A.J. Green. Almost everyone in the locker room acknowledged they could have played better in at least some small way.
The game might have aged Lewis a few years, as well. The Bengals' roster was one of the youngest in the league when Cincinnati made the initial cuts to 53 players last weekend. That means mistakes -- and lots of them.
"A lot of learning here, and that's a good thing. That's what you want," Lewis said. "We've got to be able to learn. We've just got to learn the lessons quickly, because we have a quick turnaround.'
Green offered his take.
"The first game is always an up and down roller-coaster ride," Green said. "At the end of the day, you just have to ride that wave. You have to make the play whenever your number is called, and that's what we did."