Home games being moved thousands of miles and former champions finding form as others enter a crisis.
The Champions League knockout stages have become an absolute must-watch in recent years - and it is time for the pinnacle of club football to get under way this week.
How much of a difference could Covid make and how will the English teams fare? Can anyone stop Bayern Munich?
Teams losing 'home' advantage
All three English teams have been handed a boost - from a sporting point of view at least - after their away legs were moved to neutral venues.
RB Leipzig v Liverpool and Borussia Monchengladbach v Manchester City will take place in Budapest, Hungary. That is a 1,000- and 1,500-mile round journey respectively for the German clubs' 'home' games.
Atletico Madrid's game with Chelsea next week will now be in Bucharest, Romania.
Those changes are all because of international travel being restricted between the UK and other countries because of the Kent variant of coronavirus.
As things stand all the second legs are in England but that could yet change.
Home advantage may seem less important with the lack of fans - but there were the exact same amount of home wins in the group stage as there were last season pre-Covid (40 out of 96).
The win ratio was worse in the 28 games this season with a crowd - with only seven wins - although some of the weaker teams were those allowed to have fans.
How are the English teams shaping up?
Chelsea face a tough tie against Atletico Madrid - with goals potentially at a premium. The Blues are unbeaten in six games under Thomas Tuchel, only conceding one goal. Atletico have only let in 13 goals in 21 La Liga games this season.
Frank Lampard was sacked in January despite taking Chelsea through the group stages unbeaten.
"It's a fascinating tie," European football journalist Julien Laurens said on the BBC Radio 5 Live's Football Daily podcast. "This is a much better Chelsea team than when the draw was made and Atletico were clear favourites."
Another tie where the dynamic may have shifted since the draw is RB Leipzig v Liverpool.
Jurgen Klopp's Reds have only won five out of 15 games since the end of the Champions League group stages.
"Liverpool are in crisis," said Laurens. "We never thought Liverpool would be so bad going into a game like this when the draw was made.
"It's student against master. There's a case for Julian Nagelsmann trying to outsmart Klopp tactically. It's a fascinating battle."
Manchester City - who play Borussia Monchengladbach - go into the game in record-breaking form. They have won 16 games in a row in all competitions, a record for an English top-flight side.
Pep Guardiola's side - who are second favourites to win the tournament - are still in with a chance of the Quadruple this season.
They top the Premier League and are in the FA Cup quarter-finals and the EFL Cup final.
Who are the favourites to win it?
|Chances of winning the Champions League (according to Nielsen Gracenote's Euro Club Index)|
|30% - Bayern Munich||4% - Juventus, Sevilla|
|22% - Manchester City||3% - Paris St-Germain|
|9% - Barcelona||2% - Chelsea, RB Leipzig|
|8% - Atletico Madrid||1% - Borussia Dortmund|
|6% - Liverpool, Real Madrid||<1% - Atalanta, Porto, Borussia Monchengladbach, Lazio|
Bayern Munich are the clear favourites after winning last season's Champions League and the clean sweep of all six 2020 trophies (including the delayed Club World Cup).
They are not quite at their swashbuckling best - and cannot retain their treble after a German Cup exit - but have won seven and drawn one of their last eight games in all competitions.
Barcelona failed to top a Champions League group for the first time since 2007. Things appear to be improving for them since then though. They are unbeaten in La Liga in 12 games, winning 10 of those.
This could be their final chance to lift the Champions League trophy a fifth time with Lionel Messi - if the club legend does leave the Nou Camp this summer.
They are also boosted by the absence of their former player Neymar in their last-16 tie with Paris St-Germain.
Could this finally be Atletico Madrid's year? Diego Simeone's side have only lost four games in the past 12 months in all competitions - with Luis Suarez in great form - and sit five points clear in La Liga with two games in hand.
Real Madrid, who did not seal a last-16 spot until the final group game, have lost three of their last seven domestic matches, while Andrea Pirlo's Juventus are eight points off the pace domestically.
Any potential dark horses?
Sevilla are given a 4% chance of winning the tournament by data company Gracenote - the highest of any of the teams not mentioned above.
Managed by former Spain and Real Madrid boss Julen Lopetegui, Sevilla have won nine games in a row in all competitions - including a 2-0 win over Barcelona in the Copa del Rey semi-final first leg.
Spanish journalist Guillem Balague said of the six-time Uefa Cup/Europa League winners: "They're a cup team.
"Lopetegui has rediscovered all his prestige in my eyes [after being sacked by Spain and Real]. Jules Kounde is the best centre-back in the world. He looks amazing."
Last season's beaten finalists Paris St-Germain - who are without Neymar for the first leg against Barcelona - are only given a 3% chance of glory, while Atalanta, who were one of last season's best teams to watch, are given a less than 1% hope.
They play Real Madrid, who are likely to be without captain Sergio Ramos for both legs after successful knee surgery.
Italian football writer James Horncastle said: "We've seen they've gone to Anfield and won, gone to Ajax and won. Real Madrid have been out of sorts. Their record without Ramos excites me."
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