This year, the only two teams that lost very good starting QBs were the Texans and the Colts. In both cases, they have comparable backup QBs to Hundley, but the Colts had the entire preseason to get their QB ready. The Texans are a closer fit. They were winning games with Watson at QB. Since the injury...not pretty, 1-6. The Texans also lost two pretty good defensive players in the first week, but that was quite a few games before the Watson injury.
Losing your very good starting QB is usually devastating. This year, only the Packers have been able to remotely tread water.