Williams (back) did not participate in Friday's practice and is listed as doubtful for Sunday's game in Houston, ESPN's Mike Rodak reports. Williams is a starter at guard whom the Bills recruited in free agency this season. Rookie Cyril Richardson is expected to get his first NFL start if and when Williams can't go, which would give the Bills two rookies on the O-Line. However, Seantrel Henderson at right tackle has surpassed everyone's expectations so far.