Rivers suffered the injury on the fourth play of Sunday's 38-10 loss at home against Pittsburgh when Steelers wide receiver Hines Ward blocked Rivers as Rivers was chasing after tight end Matt Spaeth following a reception. Rivers, who is second on the team with 50 tackles, never saw Ward coming back for the block.
There was no penalty called on the play, and according to NFL.com's Adam Schefter the league has reviewed the hit and deemed it legal. It was the third straight game in which Ward was involved in a hard block on an opposing defender. His hits in wins against Baltimore and Jacksonville resulted in the league fining Ward $15,000 even though he was not penalized during the games for those hits either.
Bengals head coach Marvin Lewis declined to say on Monday whether or not the hit could be considered "dirty" or not. Lewis is a member of the NFL's Competition Committee.
"There was not a foul. There were no flags thrown," said Lewis on Monday.
Third-year player Brandon Johnson will take over as the starting weakside linebacker in place of Rivers.
The Bengals made two other transactions on Tuesday. They added rookie guard Andrew Crummey (6-5, 301) to the 53-man roster after signing Crummey from the Washington practice squad. The team also released kicker Dave Rayner, who had played the last two games in place of an injured Shayne Graham. The move is a signal that Graham's right groin should be healed enough for him to resume his duties this Sunday at Houston.
The Bengals have one open spot on their 53-man roster after Tuesday's transactions.