Teammates at Barcelona for the past two seasons, they now find themselves in opposition. We asked our club correspondents to run the rule over them.
There are storylines galore when it comes to Barcelona vs. Man City but the battle of two top goalies is the one to watch, writes Graham Hunter.
ESPN FC's Sam Marsden says Barca are downplaying Guardiola's return and expect a completely different Man City side.
Monaco have suffered a few setbacks after a flying start, but two games against CSKA could have them back in business.
Arsenal won't take Ludogorets lightly even for a second, but that doesn't mean that Arsene Wenger can't shuffle his pack a little for the clash.