The draw for the Champions League round-of-16 has been made, and there's one clash that stands out as Neymar's PSG take on champions Real Madrid. But there are plenty more storylines to follow. Here's what to watch for.
Real Madrid vs. PSG
Real's punishment for finishing second in Group H could hardly have been more severe -- a tie that many would have fancied for this year's final and one that will eliminate one of the tournament's super-favourites in one stroke.
There is not much head-to-head history to draw upon, two fairly dull group stage meetings in 2015-16 aside, and this will be a matchup to sharpen the senses after both sides were dealt setbacks earlier on in the tournament. Does Tottenham's convincing win over Real suggest the champions, unconvincing this season, are there for the taking? Does the manner in which Bayern Munich defeated PSG on matchday six, avenging their 3-0 loss at Parc des Princes, bring a conclusion that Unai Emery's team are still short of making the final step demanded of them? It promises to be some ride.
Key factor: PSG bought Neymar for exactly this kind of occasion and will expect him to step up here. His record against Real while at Barcelona was reasonable, scoring three goals in four seasons; perhaps more encouraging are the six goals he scored in this year's group stage. Neymar has been linked with a 2019 move to Real in recent days: his performance in this tie will be key to their short-term fate.
Prediction: PSG progress. The French side to banish the ghosts of last season's collapse against Barcelona and -- amid a wave of hype for their Champions League prospects -- send the holders crashing out after a back and forth tie.
Chelsea vs. Barcelona
We have been here plenty of times before although not since 2012, when Chelsea memorably came through a semifinal against opponents who were close to their peak.
Antonio Conte conceded after Saturday's defeat at West Ham that Chelsea's Premier League title hopes are over; he may prefer to concentrate resources on this tie and can draw plenty of encouragement from their two group stage performances against Atletico Madrid. But the Barcelona juggernaut will be tough to stop: they have been imperious both in Europe and domestically so far this season, even if they do not quite boast the fluency of the "MSN" era, and it may take something special to break their momentum.
Key factor: Lionel Messi has faced Chelsea eight times and, remarkably, has yet to score. If they can keep him quiet again then much will rest on the shoulders of Luis Suarez, whose form has been patchy: could this be a moment for N'Golo Kante, who seems well cut out for this kind of occasion, to stick to Messi like glue?
Prediction: Barcelona progress. Much may depend on how -- and if -- Chelsea, who look a little leggy and stretched in attacking areas, reinforce during the transfer window. Bearing current resources in mind this looks like a Barcelona win, with Messi breaking that puzzling duck.
Tottenham vs. Juventus
It could not have been much harder for Tottenham than a clash with such practiced, savvy European opposition but Mauricio Pochettino's side can consider themselves well drilled. Emerging from group stage fixtures against Real Madrid and Borussia Dortmund with three wins and a draw suggests they are ready -- and last season's runners-up, whose progression was only confirmed on the final matchday, do not quite seem the proposition they would have been a year ago.
It will do little harm that, back in August, Spurs hosted Juve in a friendly at Wembley and beat them 2-0. Harry Kane and Christian Eriksen were on target that day; if they can do the same when the stakes are higher then their team has every chance of success.
Key factor: Juventus's defensive unit has not been quite as secure this season, the departure of Leonardo Bonucci hardly helping, and Kane will be licking his lips at the chance to examine it. Pochettino and Massimiliano Allegri are two outstanding tactical operators and this looks like a tie to be decided on fine details; it might just come down to who, between Kane and the similarly potent Gonzalo Higuain, is on song.
Prediction: Tottenham progress. Another tie of wafer-thin margins but Tottenham to muster an intensity Juve cannot quite handle -- going through to the last eight and adding to the sense that this year's competition will be contested by a new order.
Basel vs. Manchester City
On paper this is exactly the tie City would have wanted. Basel performed admirably to qualify alongside Manchester United, even beating them dramatically at St Jakob-Park, but they are not a serious contender for this year's trophy and City's main enemy may be complacency. They have not shown much of that, even allowing for a skeleton lineup's defeat at Shakhtar Donetsk, and Basel's best hope may be that they catch Pep Guardiola's side at the tail end of some kind of winter slump.
Key factor: Basel are no mugs. They are experienced, resolute and will make City work to break them down -- and boast the searing pace of Dimitri Oberlin, the Red Bull Salzburg loanee who had a brilliant group stage, further forward. If City are not diligent he can expose a back line that is not always the most mobile; for Guardiola and company the key will be to retain the patient, serious attitude that has brought them so far already.
Prediction: Man City progress. The away game may be closely contested but ultimately it would be a huge shock if City, who currently look the best side in the competition, do not go through in comfort.
Sevilla vs. Manchester United
It could have been worse for United, who have never faced Sevilla at any level before. The Spanish side's group stage brought 12 goals scored and conceded in their six games; it feels like a winnable tie for Jose Mourinho against a team that, just like United, has recent Europa League-winning pedigree.
Over the weekend Sevilla were pummeled 5-0 at Real Madrid; they will surely put on a better show in Europe although memories of their tie against Leicester last year, when they threw away a comfortable two-goal advantage, may loom large.
Key factor: United feel like a different team with Paul Pogba -- far more compact and with far more connection between defence, midfield and attack. Mourinho is the master of finding a way past someone, anyone, but with Pogba fit and firing his hopes of competing on equal terms with the best skyrocket. The Frenchman could well make the difference here.
Prediction: Man United progress. United to go pass a test they would probably have welcomed before the draw, although in fairly low-key fashion.
Porto vs. Liverpool
A decade has passed since these sides last faced off in the Champions League, Liverpool winning 4-1 at home and drawing 1-1 away in the 2007-08 group stage. Jurgen Klopp would settle for more of the same and Liverpool, whose 23-goal haul in the group stage was stunning, are unlikely to draw two blanks here.
The question, as ever, is how they fare at the other end and Porto -- now managed by Sergio Conceicao -- look dangerous. They netted 15 times themselves in Group G, scored eight in two fixtures against Monaco and average more than 2.5 goals a game in a domestic league they lead. Liverpool may need to defend with a level of attention that has often eluded them.
Key factor: Whether Liverpool can suppress a Porto attack for whom the likes of Vincent Aboubakar and Yacine Brahimi have been on excellent form. If they can, they are likely to have more than enough firepower to cause problems at the other end.
Prediction: Liverpool progress. The Reds to go through in one of the round's most entertaining, high-scoring ties -- but not without a scare or two.
Bayern Munich vs. Besiktas
What looks a favourable tie for Bayern may not quite be that straightforward. Besiktas are a dark horse and their investment in Champions League pedigree, with Pepe imperious at the heart of their defence, appears to have paid off. They also boast a prolific striker in Cenk Tosun who many clubs in bigger leagues would love to sign.
Perhaps the Turkish club's biggest disadvantage comes in the timing of this draw, with Bayern having improved significantly under Jupp Heynckes and performing with some sparkle in their win over PSG.
Key factor: Heynckes knows Bayern inside out and knows what it takes to win this competition, too. His experience should be enough to help Bayern through a tie that has "banana skin" written all over it.
Prediction: Bayern progress. The Germans to go through but it will not be simple... Besiktas went through the group stage unbeaten and will not go quietly.
Shakhtar vs. Roma
Neither side will be too unhappy with this tie -- but Roma will be on their guard after Shakhtar, the Ukrainian side who play 300km away from their home city in Kharkiv, after they qualified six points ahead of Napoli in Group F.
Shakhtar, managed by the excellent Paulo Fonseca, are a handful and boast some outstanding forwards in Bernard, Marlos and Facundo Ferreyra. Roma will be confident they have the requisite firepower of their own although there will be concern that the goals have dried up a little for Edin Dzeko after such a prolific start to the campaign.
Key factor: Roma would probably have preferred not to travel to eastern Ukraine, where temperatures may dip below freezing point in February. If they can escape without too much harm being inflicted then Shakhtar are a different proposition away -- as their 3-0 defeat at Napoli, who they had beaten 2-1 at home, shows.
Prediction: Roma progress. Roma to survive the odd scare and go through with a convincing home performance after drawing the away leg.