The return of the Champions League throws up some typically heavyweight clashes this week, as well as some intriguing storylines in the battle for power in Europe.
Emerging forces Manchester City, Paris Saint-Germain and Atletico Madrid are all in action with a point to prove, while Bayern Munich and Barcelona—who between them have won the competition three times in the last five years—will be keen to show why they are among the favourites for the tournament.
Read on for a profile of some of the players to watch and predictions for all this week's games.
Manchester City vs. Barcelona
Player to Watch: Alvaro Negredo
Negredo will have a fair idea of what to expect against Barcelona, having played in La Liga until last season.
With Sergio Aguero missing through injury, the responsibility will fall to Negredo to lead City's line and grab them a goal and possible victory at the Etihad.
Barcelona's defence is not as strong as it once was, and the tie could hinge on City being able to exploit their opponent's weakness and take an advantage into the second leg.
Key Player: Lionel Messi
After losing his Ballon d'Or to Cristiano Ronaldo and suffering through injury during the final months of 2013, Messi has some catching up to do.
The Argentinean will be a handful for City's defence, and stopping him will make a huge difference. With five goals in his last three games, he is in form. Given half a chance, he has the ability to put the tie to bed.
Prediction: Manchester City 1-1 Barcelona
City's achievement in qualifying from the group stage is commendable, but they will not want to depart the tournament this early.
Facing Barca seems like a chance for them to lay down a marker as to how far they have progressed under Manuel Pellegrini, but, as reported by BBC Sport, Chelsea boss Jose Mourinho has claimed this is the worst Barcelona side for sometime, saying: "Of course, they have [Lionel] Messi - he is special - and they have more than him. But I think this is the worst Barcelona of many, many years."
Expect it to be a close-run affair.
Bayer Leverkusen vs. PSG
Player to Watch: Yohan Cabaye
Making his Champions League debut at the age of 28, Cabaye will want to make up for lost time and show that the reported £20 million PSG parted with for his services is not over the odds.
Cabaye was Newcastle's standout performer this season, and the club have struggled to cope since his departure. If he can pick up the midfield maestro role he played in the Premier League, then he can run the show for PSG against Bayer Leverkusen.
Key Player: Zlatan Ibrahimovic
The real game-changer and star of PSG's show is Ibrahimovic.
Ibrahimovic has never won the Champions League and is not going to the 2014 World Cup, so success in the Champions League will mean a lot to him.
Expect the Sweden international to take it upon himself to guide PSG through to the next round with a strong showing in Germany.
Prediction: Bayer Leverkusen 2-2 PSG
Bayer Leverkusen are no pushovers, and if PSG underestimate their opponents, then they could be in for a shock. But the sheer star quality of Laurent Blanc's side means that they should have enough to progress over two legs and score a couple of away goals at the Bayarena.
Arsenal vs. Bayern Munich
Player to Watch: Thiago Alcantara
Signed from Barcelona during the summer, the Spain under-21 captain could have taken his pick of top clubs or emerged to succeed Xavi in the Barca midfield.
That he was hand-picked by Pep Guardiola to join Bayern says a lot. After getting over an injury that disrupted him at the beginning of the season, Thiago has begun to show his best form in the Bundesliga, as shown by this tweet from WhoScored:
Having never played a full role in the Champions League, the next step in his development will be to see if he can mix it with the big boys, and they don't come much bigger than Arsenal's star-studded midfield options.
Key Player: Mesut Ozil
The club-record summer signing has come in for criticism from fans and manager Arsene Wenger recently for a slump in his early season form.
The accusation leveled at Ozil is that he didn't fancy it when faced with a Liverpool team that got in his face and denied him time or space on the ball.
Bayern will know what to do to upset the Germany international, and whether he steps up will be crucial to Arsenal's hopes of progress against the European champions.
Prediction: Arsenal 1-1 Bayern Munich
Expect a tight first game with neither side willing to give much away. Bayern will be happy to come away with a score draw. If Arsenal can make it into the return leg with everything still to play for, then they too will deem the first leg a success.
An early goal would open the game up, but it is more likely to be a cagey affair that will see little given away.
AC Milan vs. Atletico Madrid
Player to Watch: Adel Taarabt
The winger, on loan from QPR, has always shown glimpses of great form and threatened to explode onto the scene but hasn't quite made it.
Given the chance to earn a contract at AC Milan and the opportunity to prove himself in the Champions League, it is time for Taarabt to fulfill the potential he showed far too rarely during his time at Loftus Road.
Milan are in need of a player to step up and share the responsibility with Mario Balotelli in attack. Against Atletico Madrid, Taarabt has the chance to show everyone he can be as good as he once promised.
Key Player: Mario Balotelli
It is a given that Atletico will turn up. They made it through the group stage unbeaten, winning five out six matches.
Diego Costa's form has been outstanding, scoring 25 times in 27 games, and their continued presence at the top of La Liga shows that they are a strong team unit.
But Balotelli has the ability to upset the applecart and prevent an under-strength Milan side in transition from being turned over and dumped out of a competition they have won seven times.
Prediction: AC Milan 1-2 Atletico Madrid
It will take some doing for Milan to get past an Atletico side enjoying the season of their lives. Diego Simeone's side are well drilled, organised and have a pedigree having won the Europa League in 2012 and the Copa del Rey in 2013.
They are unlikely to win the Champions League this season, but they will want to see how far they can go. Milan could be in big trouble if they concede early. The Spanish side have the ability to take an advantage back to Madrid.
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