You can go down playing like they do. Scoring two every time out doesn't much matter if you leak three. If they do go down, it would be a huge historic anomaly. Don't think anyone has gone down netting 50+ in 38, which is what they're on pace for.
That generally doesn't happen because defense is cheaper to add than goals. A competent, experienced goalkeeper like Begovic can be had for peanuts. Ditto for older, experienced CBs. Since teams want offensive productivity from the full backs, the lockdown ones can be had inexpensively as well. Teams are starting to figure out that a top DM is worth his weight in gold, so that can be pricy, but you can install a spine in a team without breaking the bank.
I think what's happened here is that a side that was a fixture in the top 6 failed to adjust to their new fiscal reality properly. They needed to sell two players, not one, plug the keeper hole and address some liabilities with the proceeds. I chalk that one up to pride.