Cam Heyward: I was upset about Josh Allen kneeing me in the stomach

Steelers defensive lineman Cam Heyward was flagged for unsportsmanlike conduct after a Bills touchdown pass in the third quarter of Sunday's game and he revealed why he lost his cool after the 26-7 loss.

Heyward was penalized after one of several verbal exchanges he engaged in with Bills quarterback Josh Allen, who had just thrown to Keon Coleman for the score. Heyward said he was upset about some extracurricular activity from Allen after a play earlier in the game.

Heyward said Allen kneed him in the stomach intentionally after Heyward tackled him earlier in the game.

"Ticked off the entire game because, as a quarterback, they're protected, but I'm not," Heyward said, via Brooke Pryor of ESPN.com. "It just pisses me off. . . . He even said after, 'I had to do something to get you off me,'"

Allen's media availability ended before Heyward spoke to reporters, but he did talk about the back-and-forth with Heyward over the course of the game.

"We love the competitiveness out of this game," Allen said. "He's such a great player. Sometimes, you need fire like that to get you going."

The NFL will reveal if any fines were issued for Heyward, Allen or anyone else involved in the game later this week.