All these games, I feel like the majority of people are like "yeah the Bears probably can't go in *insert city* and win" and then the Bears either do, or are really close to doing like in Green Bay.
The SF beat writers think no Kittle this week, which works out in the Bears favor because they historically struggle against TEs and Kittle has been the best one in the league for the last 2 months. He hasn't had less than 67 yards in any game since Nov 3rd and has 5 total TDs in that time span. Even if he does play, he won't be 100%.
McCaffery hasn't been McCaffery for most of the season, but he's also been healthy and had one of his best games of the season last week. He is a very tough matchup for the Bears, especially if TJ and/or Edmunds are not 100%. But Sunday was only his 4th game averaging more than 4 yards per carry. So if the Bears can manage to stop him the way a lot of teams have this year, they'll make the Niners one-dimensional. Granted, Shanahan will not stop running the ball and McCaffery is more dangerous as a receiver, but the point is, this isn't the same 49ers OL of old. Purdy is actually the best QB in the league at avoiding sacks, but the OL does allow a decent amount of pressure and Purdy can be rushed into a bad throw or 2.
On the other side, the Niners somehow have a worse pass rush than the Bears. That has led to a bottom 8 pass defense, which you hope Caleb can take advantage of for a full 4 quarters. The Niners did just allow big games on both opposite ends of the spectrum to rookie Cam Ward and then to a guy who last played when Ward was a college freshman. Not expecting Caleb to throw for 400 or anything, but I expect a much more efficient game passing than we are used to. And if Caleb does manage 300+ then 4000 comes into the picture in Week 18.
This is a very positive preview, but not going to assume the Bears will win this game at all. They are going to likely have to put up 30+ to win this game, and they haven't been consistent enough most days to do that, despite averaging nearly 26 per game. They've only scored more than 31 against the lowly Bengals D and needed all 47 of those points. Fortunately, they probably can count on Purdy giving them a turnover or two, but they can't afford to squander them or have drives slowed down by stupid penalties.