Steelers were stunned by Brett Keisel’s sack celebration penalty

Steelers defensive lineman Brett Keisel thought he had ended the Bengals’ first series on Sunday with a third-down sack. And then a flag came down that left the Steelers stunned. After Keisel sacked Bengals quarterback Andy Dalton on third down, he got up and did his signature sack celebration, in which he pretends to be…