I'm not sure I believe this affected their play THAT much. Even before the Cincy game we were losing steam & Allen was playing just OK. He had one really good game against the Dolphins near the end of the year, one pretty bad game against the Bears, and the rest was ok.
It felt like the Green Bay game was a turning point. Started off hot, then we started playing poorly, throwing a lot of INTs, and then we carried that forward to losing our next 2 games. Every game after that felt sloppy, even though we won out. Nearly every game was close, and it seemed like the team was struggling way more than normal.
Surely, Damar's injury affected them. But by the time the Cincy game came around, Damar was ok & going to games & supporting the boys again.