UEFA Champions League group stage midway review, big questions ahead of last-16

And just like that, we're already halfway done with the group stage of the UEFA Champions League. Blink a couple of more times, and it'll be over.

The first three matchdays have been filled with an equal amount of dour unpredictability -- Manchester City destroying everything in their path, Bayern Munich treating the group stages like, uh, well, like the Bundesliga -- and unforeseen excitement. Napoli have won all three matches. Club Brugge have won all three matches! Chelsea fired their manager immediately after dropping their opener to Dinamo Zagreb. Barcelona are staring down another spring spent in the Europa League. And Shakhtar Donetsk are this close to qualifying for the knockout rounds despite playing their home matches in Poland because their home country is at war with Russia.

So before the next three rounds speed by and everyone heads to the World Cup, we're going to use the midway point as a moment to take a quick step back and look at what's at stake over the next month of matches. With the help of the probabilities from FiveThirtyEight's prediction model, here are the biggest questions facing all eight groups.