In fact, the opposite is true. Chelsea have no hopes in the Premier League as they have already lost almost as many points as a champion can afford to lose points in a whole season and in the Champions League they are on equal footing. Therefore, it would be logical to try to get into the top 4 in the Premier League, and to perform as well as possible in the Champions League. Such a task looks more realistic than trying your best in the Premier League with so many lost points.
Honestly Chelsea opportunity with Primer League tittle winning almost close after remaining many 16 points from Arsenal, I don't think easy catch up with many points left actually after World Cup have busy match and focus at champion league. Graham Potter has best alternative option if want longer existing become Chelsea manager by priority with Champion League competition. I think realistic with Chelsea focus on Champion League than Primer League with many points left but can reach top fourth standing position.
Dortmund opponent at 16 round I don't think heavy for Chelsea based on inconsistency performance at Bundesliga, Chelsea need priority Champion League in this season if won't close season 2022/2023 without any trophies yet.
The problem of the fight for the title is not in the number of points to the first place, but in the fact that there are 7 (!) teams ahead of Chelsea. From Chelsea's point of view, you can wait (hope) that Arsenal will fall into a crisis and it will be possible to catch up with it, but to expect that as many as 7 teams will fall into an unprecedented crisis is naivety. Borussia is a random team, so it can lose big to Chelsea, but there are also chances (even for a big win). And on paper, Chelsea are stronger.