Who should you be paying attention to in the knockout stage of the Champions League?

Let's start with Zlatan Ibrahimovic. He is crucial for PSG’s attack. So far in the Champions League, the Sweden international has two goals and five assists. Not too shabby. The big man with an even bigger personality is a great leader for this relatively young side, and if he gets hot – watch out.

Want to know who else is worth keeping your eye on? Read on to find out.

The Brazilian forward scored four goals for Valencia in the group stages, and will be crucial moving forward. His partnership with Roberto Soldado will be crucial to Valencia's hopes of progressing to the quarter-finals.

Yilmaz is the joint top goal-scorer in the group stage with Cristiano Ronaldo, both having scored six goals. He will be key to Galatasaray's chances of getting into the last eight. The Turks have landed a favorable draw in Schalke but will still need Yilmaz to be in top form.

If you watched Celtic’s epic win over Barcelona, then you saw the heroic effort put in by Forster. He made save after save to keep the Spanish giants at bay. If he can put in another incredible performance in the knockout stage, Celtic will have a fighting chance to move on to the next round.

The Brazilian has been a key component in Shakhtar’s success in the Champions League thus far. And his pairing with fellow Brazilian Fernandinho has created a strong midfield – and one that many big clubs across Europe have been eyeing. Reports have both Brazilians linked with teams like Manchester United and Chelsea.

The young Italian striker has been turning heads over the last few months and is a hot transfer market target for a reason. Not only does he score goals, but he is relentless all over the pitch – his constant hard work on defense paired with his offensive talents make El Shaarawy one to keep an eye on in this round of play.

Yes, Arsenal have had their ups and downs across all competitions this season, but one general consistency has been Cazorla. The Spanish midfielder has all the ability in the world, and can both create goals and score some magnificent ones. If he can jump-start the Gunners’ offense in the knockout stage, the midfield magician will help lead Arsenal deep in the competition.

The young, talented Colombian got off to a bit of a slow start in the Champions League, not scoring his first goal until match day three, but scored a total of three goals in the group stage. If he can continue to find the back of the net for Porto, their hopes of making it out of the knockout round could become a reality.

Center back Jerome Boateng is suspended for the next round and with Holger Badstuber sidelined for the year, it may be up to Martinez to step in alongside Dante. The defensive midfielder will be critical in shoring up the backline and protecting Bayerns' aggresive attack until Boateng gets back.

It’s easy to point to veteran Andrea Pirlo or Claudio Marchisio as the key to this Juventus side, but it’s the performance of Vidal that could really top the balance in Juve’s favor in the knockout stages. He had three goals and two assists in the group stage, and should he continue his form while surrounded by the previously mentioned midfield maestros, Juventus could make a strong push through the knockout round.

We all know Dortmund’s attack is lethal (See Reus, Gotze and Lewandowski) and the defense is stout (Hummels, Subotic), so it will come down to the midfield play to see how far BVB can go. Gundogan was brought in to replace Nuri Sahin and after a so-so first season with the club, he has enjoyed a great 2012, starting nearly every match and earning national team call-ups. He is the link between the two strong points in Dortmund’s game.

The 20-year old midfielder has two goals and three assists so far in this Champions League campaign. Even at a young age, he has shown maturity and composure that Malaga will need in their round of 16 clash with Porto.

The Dutch striker will be critical in scoring for Schalke in the next round of the Champions League. Right now, the team is in a bit of a crisis that has cost Schalke coaching leged Huub Stevens his job. Huntelaar has also reportedly agreed to an extension, which could provide extra motivation to lift the club out of its funk.

Manchester United’s defense still lacks consistency, but Robin van Persie has been the opposite: United can always count on him to get the job done offensively. As long as he can stay hot alongside Wayne Rooney, United will have a shot at getting into the next round – they may give up a few goals, but they’ll have no trouble scoring more than they let in.

The Portuguese forward will need to show up and have a strong performance to help lift Madrid out of its slump. The club has struggled during a season in which Barcelona is running away with La Liga. Could their league woes help motivate Ronaldo and Madrid in the Champions League? Probably, and that’s why no one wants to face the Spanish giants in the knockout stages. Despite their poor form as of late, this team is stacked with talent.

The goal-scoring machine will lead Barcelona’s offensive efforts in the knockout stages. It is almost a guarantee that Messi will show up and score (or at least assist), so you won’t want to take your eyes off the little genius in the next round.