Sergio Aguero will provide the biggest threat to Barcelona.
The Blaugrana will certainly not be relishing the two matches against Manuel Pellegrini's swashbuckling, rampaging City side. Whilst Pellegrini failed to beat Barca over four games last season when in charge of Malaga, his knowledge of the Spanish league and in particular Barca's style of play, will be invaluable.
Man City v Barca: Aguero v Messi Neymar v Nasri Iniesta v Silva Yaya Toure v Xavi Kompany v Pique... pic.twitter.com/1eAXM5RK9u— Footy Humour (@FootyHumour) December 16, 2013
For their part, the Catalans have never really fared too well against teams full of tall, strong and physical players and Tata Martino will have his work cut out in guiding his team through the two legs to the quarter finals and beyond.
Clearly, one of the main threats to Barca's progression will come from the dreaded high ball into the box. Martino, like many before him, is no closer to mastering that one simple act of defending. Manna from heaven for Pellegrini's charges.
Toure, Alvaro Negredo, Vincent Kompany and others will give the Blues a significant height advantage, so Martino's choices at the back are crucial.
City's biggest threat comes from the in-form Sergio Aguero, whose partnership with Negredo is one of the chief reasons for their recent climb up the Premier League table, and the 11 goals between them in the Champions League speak for themselves.
Currently injured, you can be assured that Aguero will move heaven and earth to ensure his availability for the two games. Similarly, compatriot Messi will want to prove he is back to his very best after a few months punctuated by injury concerns.
In midfield, Pellegrini has the luxury of a wonderfully gifted and creative pair in David Silva and Samir Nasri supplemented by a strong and mobile core in the central areas. Yaya Toure was the catalyst for City's first Premier League title win and continues to excel, whilst the addition of Fernandinho alongside the Ivorian has been a masterstroke.
The Brazilian was head and shoulders above everyone on the pitch in the recent 6-3 win over Premier League leaders Arsenal and his industry alongside Toure should keep the probing from Xavi Hernandez and Andres Iniesta to a minimum.
The games are likely to be won and lost in the midfield so it is crucial that Barca impose their passing game quickly and efficiently.
A towering central defensive unit consisting of Vincent Kompany, Martin Demechelis and others are unlikely to give much away aerially, Barca's best chance to register perhaps coming via the flanks.
Dependant on Martino's school of thought, the trickery of Neymar, pace of Pedro Rodriguez or industry of Alexis Sanchez should all pose significant problems for Pellegrini's selections in the full back areas.
Costel Pantilimon's consistency between the sticks over the next few weeks will dictate whether Joe Hart claws his way back into the reckoning for Pellegrini. It's an area where the managers policy of using one keeper for the EPL and another for the UCL is benefiting no one at the Etihad presently.
Pellegrini needs to be clear as to his selection in this area well before Barca visit Manchester, with the Blaugrana adept at exploiting any weaknesses or nervousness.
Over the course of two legs, Barcelona will feel they still have the edge to knock out their less experienced opponents, but they underestimate a strong City side at their peril.