PITTSBURGH -- The Detroit Lions' defensive line broke an unwritten NFL rule Sunday when it fired off the ball on a kneel-down play, said Steelers center Maurkice Pouncey, who was incensed by the play one day after Pittsburgh's 20-15 victory at Ford Field.

With 48 seconds left in regulation, the Steelers were downing the ball to run out the clock when tackles A'Shawn Robinson and Akeem Spence appeared to attack the Steelers' interior line. Pouncey retaliated, and Robinson was ejected for throwing a punch at guard Ramon Foster. Pouncey said hitting on a kneeling play is dirty enough to warrant a suspension.

"You have to show sportsmanship," Pouncey told ESPN. "You just lost the game. We're taking a knee. What are you trying to prove right now? If anybody's playing [dirty], that's dirty s--- right there. They literally tried to attack me, come off 100 miles per hour. I ain't going for that ... Do it during the game. You want to do it while we're taking a knee? It's a general rule of sportsmanship. You don't do that type of s---."

"You just lost the game. We're taking a knee. What are you trying to prove right now? If anybody's playing [dirty], that's dirty s--- right there. They literally tried to attack me, come off 100 miles per hour."

Three Lions players left the sideline during the skirmish, which is against NFL rules. Lions coach Jim Caldwell planned to address the matter with his team, saying, "We're not going to stand for it."

The Lions weren't happy with the Steelers' line play, with Spence saying after the game that Pittsburgh players executed some high-low blocks and cutting methods.

"I looked on the big screen, and it looked kind of crazy. It was like I beat him, then Foster came on me. Then Pouncey came to dive at my legs to try and help Foster out. I thought it was kind of dirty. But, I mean, it's football," Spence said.

Asked about the accusation, Pouncey said, "I don't care what they say. Go watch the film. They were getting balled on."

Spence said he told Steelers guard David DeCastro before Pittsburgh ran its victory formation plays that he would be coming off the ball and that he does that because "what if they handed it off." He does this, he said, to make sure the opponent takes a knee and that you never know if there will be a botched snap or a ball will be dropped. If he didn't go hard and that happened, then he would be blamed then, too, particularly in a one-score game.

Spence was a rookie on Greg Schiano's final Tampa Bay Buccaneers team in 2013 -- and one of Schiano's late-game tactics was to sometimes blitz during an opponent's victory formation. Spence said Sunday what he did was nothing close to that.

"Nah, we used to go at people's legs, which I thought was really cheap," Spence said. "It wasn't nothing like that. Just came off with my hands up high, just playing ball. Nothing crazy. Nothing out of the ordinary. Just got a little chippy."

Pouncey pointed out the game wouldn't have been as close if the Steelers didn't drop two would-be touchdowns. Eli Rogers dropped an end-zone pass on the opening drive, and Ben Roethlisberger overthrew Darrius Heyward-Bey on another.

Pouncey didn't want to swing at Robinson but felt there was "no turning back" after the Lions came at him.

"I don't even play dirty like that, but once someone does some cheap s--- like that, that's some bulls---. I can't respect a man like that," Pouncey said. "Knowing we're just about to snap the ball and stand there and you want to fire off? That's player safety. It's a general, common thing. What if I just fired off the ball and cut him?"

ESPN's Michael Rothstein contributed to this report.