Pep Guardiola's homecoming

Arguably the only meeting of true heavyweights this week, and inarguably the game of the round, but then this match is about so much more than this Champions League group and Manchester City trying to make up two points on Barcelona.

It is about Pep Guardiola's return home to Barcelona, and everything that entails. It also feels like his first real test as to where exactly his City team are. Even though they have played Manchester United and Tottenham Hotspur in the league, and some of the sheen has gone now that they've dropped four points from the last six, it's quite clear that Guardiola's side are Premier League favourites.

It's still unknown, however, how good they are compared to Europe's true elite; compared to one of the clubs whose current prestige Guardiola helped construct. Matching sides like Barcelona, after all, is precisely why City appointed the Catalan and essentially restructured the club so it resembles what happens at the Camp Nou.

The irony is that Barca's evolution under Luis Enrique means that City now probably play a more consciously Barcelona style than the club who bear the name but, as Guardiola found when he went to the Camp Nou with Bayern Munich in May 2015 and lost 3-0, that may not be enough. Even if you try and keep the ball away from them, it's very difficult to keep Neymar, Luis Suarez and Lionel Messi out. This will show whether City have really started to catch up.

Can Celtic or Gladbach take advantage?

The meeting of Barcelona and City actually gives Borussia Monchengladbach's trip to Celtic added importance.

There is a chance for one of them to put proper pressure on the big two. Celtic will already be emboldened by their fine 3-3 draw against City and a win here could suddenly change the complexion of this group. Even if the expectation would still be that Barca and City will cruise through -- regardless of what happens between them -- the sudden pressure of having teams within a point or two can make things more complicated.

Monchengladbach are just hoping for their first point. Yet, even though we're already at the third game, that could still mean they're within a win of second place. As a consequence of all that, this is likely to be a lively game, and one with edge.

Can Carlo Ancelotti recover Bayern Munich's verve -- and get a victory?

All of a sudden, Bayern Munich have become all too mortal. They're finding out what it's like to not win almost every week and, having not won any of their last three games, chairman Karl-Heinz Rummenigge doesn't like it all too much.

After their latest dropped points, a 2-2 draw with Eintracht Frankfurt in the Bundesliga, he said: "That wasn't Bayern Munich in the first half, we can't play like that. It was unacceptable, we have to go out on the pitch with a different attitude."

They are strong words, that seem a little over the top when you consider that they have only drawn two successive league games and were beaten by a brilliant Atletico Madrid in the Champions League, but it's not just about results, or even form.

Something looks off from the way they're playing. They lack a level of integration and intensity. Those are traits that Ancelotti has been accused of lacking as a manager in the past, and are often seen as big factors in why he has a surprisingly poor league record, with only three domestic titles in almost 20 years at top clubs.

This drop-off could be evidence of that, or it could just be evidence of an inevitable readjustment as they go from a manager with one very distinctive style in Guardiola to another. It does mean they're behind Atletico in this Champions League group, though, and could do with a win over PSV Eindhoven at home to get on track -- and try and get back to where they're used to: leading from the front.

Leicester of old to continue Champions League adventure?

After the English champions' latest domestic defeat at the weekend -- the 3-0 loss away to Chelsea also marking the third time this season that they have lost by three goals -- Claudio Ranieri made an admission: "You see a different Leicester, and so do I and my players. Are we thinking more about the Champions League than the Premier League?

"I know it's normal that, when a team goes into the Champions League for the first time, the concentration is very high in Europe. It's not the same in the Premier League."

So, will it continue in that vein against Copenhagen, especially since a win would effectively seal Leicester's place in the round of 16 -- or will the difficulties of the last few league games start to tell? The difference in performance will certainly be something to watch, as Ranieri tries to figure what changes from one game to the next, and one competition to the next.