That honor belongs to the 1969 Chicago Bears, a team that finished 1-13 for the worst single worst season in franchise history. While it may not make us feel too much better about our current squad, it is nice to know that it's been worse.
The 1969 Bears were blown out by 14+ points seven times that season, and the only win of the season came from the only team having a worse season than them, the Steelers. The bigger kicker here is that because of that win they lost the chance to draft Terry Bradshaw and struggled for a few more years as Pittsburgh flourished.
So maybe we have no receivers, and Fields is missing the last game, it'll be okay. Why? Because it's been worse.