At last, the Champions League knockout rounds are upon us and the competition begins to take on its old-style European Cup format. There is always drama and controversy in the round of 16, and this week's ties sees two of Europe's best teams lock horns with Premier League giants still dreaming of a first Champions League title.
Here is what to look out for in this week's games:
Manchester City vs. Barcelona, Tuesday
When the draw was made, this fixture forced everyone to say, "Well, let's wait until the match comes around and then we'll see what kind of form the teams are in." Now that time has come, and it's still hard to predict the outcome.
What we do know that is that both teams look like peaking just at the right time: this Barcelona is stronger than the one that lost 3-2 at home to Valencia a couple of weeks ago, strengthened by the return to fitness, and form, of Lionel Messi.
The memory of City losing 2-0 to Chelsea and drawing 0-0 at Norwich has been eroded by the weekend's comfortable win over Chelsea.
This is the key moment for the South American coaches at both sides: for Barcelona, Tata Martino has rotated his team all season to ensure freshness for this period -- "we will see less turnover, now, I'm sure," he told the Spanish press last week -- while Manuel Pellegrini will look to exploit Barcelona's weakness in the air, with Alvaro Negredo and Edin Dzeko an option to start together.
City's problem is more short-term, but arguably greater: it will be without Sergio Aguero, its best player, for the first leg, and without him, is a totally different proposition. City could also miss Fernandinho in midfield, leaving Pellegrini to choose between Martin Demichelis, James Milner, Javi Garcia or Jack Rodwell as Yaya Toure's midfield partner.
The Aguero factor could decide this tie. If he is back for the return leg, he could trouble Barcelona at Camp Nou; before then, City has the small matter of Messi, Neymar and the prolific supporting cast of Pedro (16 goals) or Alexis (15) with which to contend.
Decisive player: Yaya Toure, Manchester City. This is the first time Yaya has faced his former side, with whom he has a complicated relationship. He loved his time there and was part of Pep Guardiola's six-trophy season, but claimed he was dropped for Sergio Busquets purely because he was a graduate of the famed La Masia academy.
"I feel more valued at City because at Barcelona I was forced to play in just a defensive position while at City I have the freedom to go anywhere," he told ESPN Brazil earlier this season. Without Fernandinho beside him, Yaya has looked a different player and he will have his work cut out at his former club.
Tipped to progress: Barcelona, in a high-scoring tie
Bayer Leverkusen vs. Paris Saint-Germain, Tuesday
This is a clash of cultures as well as philosophies: Leverkusen has a reputation as the 'losers' of the German game, with its last trophy in 1993 (the German Cup), and it has finished second in the Bundesliga five times since 1997. Sporting director Rudi Voller is happy with European qualification every season and, with a €60 million annual budget that's the seventh highest in the Bundesliga, its underachieving tag is unfair. Leverkusen is the last team to beat Bayern Munich in the league, back in October 2012, and currently sit in second place.
"We have nothing to lose, Paris is one of the top five teams in Europe," Voller told L'Equipe Monday.
For big-spending PSG, the stakes are higher: five points clear in Ligue 1, the target this season is to improve on last year's Champions League quarterfinal spot, when it was only eliminated by Barcelona on away goals.
Captain Thiago Silva has spoken of reaching the final this season, while the club is mindful of president Nasser Al-Khelaifi's ambition, on taking over: To win Ligue 1 by 2013 (it did) and compete for the Champions League by 2015 (it's on course).
PSG is the form team, while Leverkusen, dumped out of the German Cup by second division Kaiserslautern last week, is on a run of five losses in seven games. It's also missing influential midfielder Emre Can through suspension.
Decisive player: Zlatan Ibrahimovic, Paris St.-Germain. Ibra is averaging almost one goal per game for PSG, but more than that is his influence on the whole club: a popular figure who has the ear of Al-Khelaifi. The one blot on his CV, for all the league titles in his career (since 2002, his team only failed to finish top once, with Milan in 2011-12), is in the Champions League. He has only reached the semifinals once, in 2010 with Barcelona, and historically his goal output has dropped in February and March.
One theory that did the rounds in Italy was that his physique was not suited to winter's hard and heavy pitches, but last year his February tally of four was the best of his career. His needless last-minute red card against Valencia at this stage of the competition last season almost cost PSG dear: the French champion could be a dark horse for the competition if Zlatan is on form.
Tipped to progress: Paris Saint-Germain
AC Milan vs. Atletico Madrid, Wednesday
Spanish title challenger Atletico Madrid ended a run of three straight losses with a comfortable 3-0 weekend win over Real Valladolid but the best news for coach Diego Simeone was the return from injury of David Villa and Thibaut Courtois.
"Every team has a difficult spell and we are perhaps a little tired," Simeone confessed to Gazzetta dello Sport last week.
Brazilian left back Luis Felipe, one of Atletico's unsung heroes, is out with a muscle tear, and midfielder Tiago is also missing.
Milan's problems run deeper than a few injuries: new coach Clarence Seedorf is still coming to terms with the challenge ahead of him since replacing Maximilliano Allegri last month, and while he has changed Milan's formation to a 4-2-3-1, performances have hardly improved.
Its 1-0 league win over Bologna on Friday night was down to a moment of improvised genius from Mario Balotelli, whose stunning 35-yard shot three minutes from time proved to be the match-winner. The fact that Milan's current captain is Philippe Mexes, the central defender prone to glaring errors and outbursts at officials, is, in some quarters, seen as summing up Milan's current plight.
Seedorf has a storied history in this competition -- he was the first player to win the trophy with three separate teams -- but if his love affair is to continue, it might not be this year.
Decisive player: Koke, Atletico Madrid. The Spanish midfielder has been tipped for the top by Simeone, and has been linked with the likes of Chelsea and Manchester United all season. His partnership with Diego Costa has been central to Atletico's success this season and that link-up has been noted by Spain coach Vicente del Bosque, who could well include both in his World Cup squad (it seems obvious, but so few other national team coaches try and replicate club partnerships in country colors; surely the fact Spain's team has in the past mainly come from two clubs has helped it win three tournaments in a row?).
Tipped to progress: Atletico Madrid, comfortably
Arsenal vs. Bayern Munich, Wednesday
Arsenal's Invincibles side of 2003-04 went the Premier League season undefeated, and comparisons have been made to this Bayern Munich side, whose unbeaten Bundesliga run is now 46 games (Arsenal went 49 games in all) and has played its toughest opponents away from home already this season. The big difference between the two: Arsenal never won a European trophy, while Bayern, defending champion, can become the first side to successfully defend its European crown since AC Milan in 1990.
Bayern coach Pep Guardiola has warned against complacency by saying the unbeaten season won't happen. And he has arguably improved on Jupp Heynckes' treble-winners of last season by constantly tinkering for the perfect formula. This has involved switching fullback Philipp Lahm to holding midfield, midfielder Javi Martinez to ball-playing center back and, at times, Mario Gotze as a false No. 9. The changes keep the players on their toes, as does the painful memory of Bayern's Champions League final defeats of 2010 and 2012.
Guardiola and Wenger may share a football ideology but the methodology is different: while Guardiola is an obsessive, Wenger's biggest knock is that he has a Plan A but no Plan B (Guardiola will have Plans B, C, D, E and F). And while Bayern's strength in depth is scary, Arsenal has looked a different proposition, a weaker one, in the absence of the injured Aaron Ramsey and Theo Walcott.
Wenger's attitude will be to try and attack Bayern but that could be dangerous: give Bayern any space and, even though it is without Franck Ribery, it can punish you. Arsenal's open style of play will suit Bayern down to the ground, and just as it dominated in a 3-1 win at Emirates last season, it might try and end the tie this week. As for whether anyone can stop Bayern: it might find life tougher against a more defensive set-up, like Chelsea or indeed Paris Saint-Germain. For now, though, this is a tie that will suit Guardiola far more than Wenger.
Decisive player: Arjen Robben, Bayern Munich. The Dutch winger scored in Bayern's Champions League final win over Borussia Dortmund last May and his return to the side after an injury layoff in the last few weeks has been seamless. His pace gives Bayern something that Arsenal, in the absence of Walcott, lacks, while his ability to burst behind defenders has been used by Guardiola as part of Bayern's more direct strategy. Witness his goal last week against Hamburg, when he ran onto to Toni Kroos's 50-yard pass to score. Arsenal will need to close down Dante to prevent him trying a similar move.
Tipped to progress: Bayern Munich