Champions League preview: 3 key matchups to watch this week

The Champions League resumes this week with a number of delicious matchups that will feature some of the tournament's most fancied sides going up against one another in group action.

Before the slate of kick-offs, we take a look at some of the individual player battles that will determine which teams walk away with three points, and which will leave their respective contests in disappointment.

Here are three key matchups to keep an eye on over the next two days.

Barcelona vs. Paris Saint-Germain: The midfield trios hold the answers

Robbed of the opportunity to watch Zlatan Ibrahimovic torment his former side due to an ill-timed heel injury, we will be forced instead to focus on the battle in the centre of the pitch.

Given the six players on display in that area, it's not exactly a punishment.

Barcelona's silky smooth trio of Andres Iniesta, Sergio Busquets and - who has fit in seamlessly with his new team - will look to break down the more physically commanding group of Thiago Motta, Blaise Matuidi and Marco Verratti.

While solely categorizing the Paris Saint-Germain triumvirate as such is unfair - they can more than hold their own in terms of individual skill on the ball - asking them to try and dominate possession against Barcelona is unreasonable. 

Instead, if the three men, Verratti in particular with his ability to snip at the heels of opponents and win possession high up the field, can turn defense into attack quickly by sending balls out wide to exploit the space behind the ultra-attacking Barcelona fullbacks, the Parisien side could be the first team to score against the Spaniards this season.

Keep an eye out for Matuidi's rampaging late runs into the area, as the Frenchman has shown on multiple occasions that is he is not tracked into the area by an opposing midfielder, he knows how to find the net.

Of course, Lionel Messi and Neymar could dominate this match on their own, rendering this analysis useless, and not a single soul would be surprised.

Manchester City vs. Roma: Toure and Nainggolan go toe-to-toe

As is generally the case (see above), matches are won and lost in midfield. It's no coincidence that the top teams in England, Spain, Germany and Italy all boast the best midfield groups in their respective leagues.

Tuesday's match at the Etihad between Manchester City and Roma will provide yet another example of the necessity of winning the midfield battle in order to be successful.

Yaya Toure came under intense criticism for his lackluster performance in City's 1-0 loss to Bayern Munich on Matchday 1, and while much of that was probably over the top considering his team as a whole was completely outplayed on the day, it's an indication of just how highly Toure is regarded that he is expected to dictate each and every match he plays, regardless of the opposition.

The powerful Ivorian, whose skills on the ball are far too often overlooked for his impressive physical attributes, will get another chance to put in a marquee performance in the Champions League today, when he and City battle a Roma side whose undeniable strength lies in midfield.

Despite the long-term absence of Kevin Strootman and the relatively recent announcement that Daniele De Rossi will also be sidelined for the contest, the Italian side boasts strength in depth, with the serviceable Seydou Keita and Serie A's early revelation Radja Nainggolan set to partner Miralem Pjanic.

The latter will get highest up the pitch and be tasked with creating chances, and Keita will act as the prototypical destroyer, but it is the Belgian who will be in direct opposition of Toure for much of the match. Nainggolan, assumed to be the primary bench option in an already loaded midfield when he arrived from Cagliari in January, has been thrust into the spotlight with Strootman still working his way back from the knee surgery that forced him to miss the World Cup.

Now there are questions of whether the Dutchman can regain his place in the squad when healthy, given Nainggolan's brilliant start to the season. Averaging 2 key passes per match while also putting in plenty of defensive work with 2.8 tackles and 1.6 interceptions per contest this season, Nainggolan's impressive work rate will see him not only attempt to bypass Toure going forward, but also slow him down before he gets to Keita in the other direction.

Atletico Madrid vs. Juventus: Mandzukic and Chiellini set to renew pleasantries 

This one should be fun, in the kind of way that watching two boxers or MMA fighters hammer away at one another is enjoyable.

While it's unlikely that we'll see any punches thrown in Madrid today, you can never rule out the possibility when these two men are involved. Juventus' stalwart defender has long been known for his strength in the tackle and willingness to put his body at risk to win 50-50 balls. He has no problem taking out the opposing attacker to do it, either.

Mandzukic, meanwhile, is lauded for his incomparable work rate as much as he is for his finishing ability, and Atletico's pressing game does not work unless it begins with the striker. In that sense, the Croatian is the perfect player for Diego Simeone's system.

Opposing teams have finally started to realize that Chiellini, often a danger to his own team with the ball at his feet, is the weak-link in Juventus' methodical passing game that requires the three centre-backs to see plenty of the ball. This was painfully obvious earlier this month against Milan, who were happy to sit back until the ball was shifted left to Chiellini, at which point their closest attacker would close down quickly to force a mistake. It worked multiple times, despite not resulting in a goal - Juventus won the match 1-0.

Mandzukic, who himself embraces the physical aspect of the game and will never shy away from a strong tackle - though both he and Chiellini have developed an annoying habit of rolling around and embellishing contact when fouled - will be the first to hassle the Juventus defenders when they are in possession.

That pressing system should create opportunities. Whether they can take them and become the first team to score against the Italian champions this season remains to be seen.