What can happen...published at 19:47 Greenwich Mean Time 16 December 2021
Wolfsburg v Chelsea (20:00 GMT)
Chelsea, Wolfsburg and Juventus can all go through from Group A tonight.
That much is clear. The details are a little more complicated.
Chelsea know that a knockout spot will be guaranteed if they avoid defeat. If they are beaten, they can still finish second if Juventus lose to Servette, a side that is yet to pick up a point in the group stage.
If Chelsea lose and Juventus win, then we wade into 'ranking' territory and it all comes down the game in Wolfsburg.
The stakes are high, indeed.