Hard to put a lot of blame on a defense that was missing their two best secondary players and only gave up 17 points, but:
1) they still should have been able to manhandle the Browns offense (specifically the OL) and they did not
2) they forced 0 turnovers from a team that was averaging more than 2 turnovers per game
3) they folded when they were needed most – down just 4 with the Browns pinned on their own 9 yard line, the defense allowed Hoyer to lead the Browns on a 91 yard, 6:37 4th quarter drive to put the game out of reach (his 2nd 90+ yard TD drive of the game.
The Defensive Line
Many have called this Bengals DL the best in the NFL (myself included). 3 sacks generally would be considered good, but not for this DL facing this Browns OL. The Browns were surrendering nearly 5 sacks per game, so to get just 3 is disappointing. More disappointing was the amount of time Hoyer had in the pocket for most of the day. The depleted secondary needed help from the DL and they did not provide enough of it.