Coming off 'unacceptable' performance last season, Bears' defense is vulnerability until it proves otherwise

It’s always prudent to rein in the optimism when it comes to the Bears. Four decades of high expectations crashing down ought to be enough to learn that lesson. It’s never popular to deliver that message, of course, and now seems like especially bad timing. The team is fresh off its first playoff win in 15 years, quarterback Caleb Williams’ stardom is surging and coach Ben Johnson has a wealth of credibility in the bank. But what about that defense? It’s the vulnerability that few outside Halas…