A horrific Sunday for the Pittsburgh Steelers appears to be a full-blown nightmare.

FOX Sports NFL Insider Alex Marvez has confirmed previous reports that All-Pro running back Le'Veon Bell will miss the rest of the season with a knee injury.

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FOX Sports NFL Insider Mike Garafolo reported the injury is "likely" a season-ender and that former Rams running back Isaiah Pead will likely be brought in for a workout.

Bell suffered the injury during the second quarter of Sunday's 16-10 loss to the Bengals when his knee bent backward while being tackled on the sideline following a catch. Bengals linebacker Vontaze Burfict, who made the tackle, appeared to celebrate with teammates on the other side of the field well after the play, catching the ire of Steelers players following the game.

Before news of the severity of the injury, Bell tweeted a thank you to fans.