According to a Tweet from Bengals.com's Geoff Hobson, Bengals head coach Marvin Lewis has stated that there is no time table on when outside linebacker Keith Rivers will get back on the field but he will not be making his way on the field this weekend in Seattle when the Bengals play the Seahawks.
Rivers is currently on the Reserve/Non-Football Injury list, which he was placed on in response to the news that he had to undergo a surgery to repair his injured wrist. The team signed Thomas Howard to a two-year deal to take Rivers' spot while he was injured but Howard has played so well through the first six games of the 2011 season that it's currently unclear as to whether or not the Bengals will bring him back to the team this year.
Both Howard and Manny Lawson have been big reasons that the Bengals have the second-ranked defense in the NFL and it wouldn't be surprising to hear in the next week that Rivers is being placed on Injured Reserve.