The path to the 2020-21 Champions League final in Istanbul has now reached the knockout phase and the draw for the round of 16 has thrown up some truly heavyweight encounters, with Barcelona vs. Paris Saint-Germain emerging as the outstanding tie with Lionel Messi and Neymar going head-to-head for a place in the quarterfinals.

Atletico Madrid vs. Chelsea will see Diego Costa return to Stamford Bridge for Diego Simeone's side, while Cristiano Ronaldo has the chance to play in Portugal once again following Juventus' pairing with FC Porto.

Reigning champions Bayern Munich will expect to overcome Lazio to reach the quarterfinals, while Real Madrid and Manchester City will believe they have a strong chance to progress at the expense of Atalanta and Borussia Monchengladbach respectively. There is also an intriguing match-ups between RB Leipzig and Liverpool, while reigning Europa League champions Sevilla take on Borussia Dortmund.

But ties which look like they may go a certain way now could be a completely different story by the time the games come around in February. So much can change -- form, fitness, managers -- while the ongoing impact of the COVID-19 pandemic ensures that nothing can be taken for granted. But with two months until the Champions League returns, here is ESPN's way-too-early look at how the ties will shape up and play out.

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Borussia Monchengladbach vs. Manchester City

Manchester City have become an experienced Champions League force under Pep Guardiola, but they have never gone beyond the quarterfinals under the former Barcelona and Bayern Munich coach and have only reached the semifinals once, under Manuel Pellegrini, in 2015-16. At some point, it surely has to be their year. City have made an unconvincing start in the Premier League this season, but they cruised through Group C with five wins and a draw and will be relieved to have avoided the likes of Barcelona and Atletico Madrid in the round of 16.

But Gladbach will worry Guardiola because of their unpredictability. Marco Rose's team hit 10 past Shakhtar Donetsk over their two group games and held Real Madrid to a draw in Germany before losing their final two games at home to Inter Milan and in Madrid. French striker Alassane Plea is the threat to City, having scored five goals in the group stage, but the reality is that the English team should win this tie comfortably.

Who qualifies?: Manchester City

Lazio vs. Bayern Munich

It will be the shock of the 2020-21 Champions League so far if Lazio, in the knockout phase for the first time since 1999-2000, can eliminate champions Bayern when the two clubs meet for the first time in competitive action. Simone Inzaghi's team were unbeaten in Group F, finishing runners-up to Dortmund, but they managed just two victories in six games. Their 3-1 win at home to Dortmund will alert Bayern to Lazio's ability, though, and the Italians will always carry a threat if striker Ciro Immobile is fit and available.

But Bayern are once again looking like the team to beat in the Champions League. They hit 18 goals in six games in Group A and topped the section with a staggering seven-point lead over Atletico Madrid. If fans are allowed back inside the Stadio Olimpico in big numbers by the time the first leg comes around in February, Lazio may be able to pull off a surprise win, but it's almost impossible to imagine Bayern failing to progress from this tie over two legs.

Who qualifies?: Bayern Munich

Atletico Madrid vs. Chelsea

Chelsea have shown signs of becoming a force again under Frank Lampard this season, but their tie against Atletico will be an acid test of their progress. Former Chelsea striker Diego Costa is battling injury problems that have kept him on the Champions League sidelines so far this season, but he is hoping to be fit within a month, so could yet face his old team alongside Luis Suarez. But the real threat posed by Atletico comes in the form of Joao Felix, the Portuguese forward, who is now justifying the €126 million price tag following his move from Benfica in 2019.

Having beaten Liverpool over two legs at this stage last season, Atletico will be confident about securing a similar result against Chelsea, who are still developing under Lampard. Two months out, this feels like a game where the experience of Atletico and Simeone will prove too much for Chelsea and Lampard, but it's a close one to call.

Who qualifies?: Atletico Madrid

RB Leipzig vs. Liverpool

Liverpool manager Jurgen Klopp will be wary about the clash with Julian Nagelsmann's Leipzig because the German outfit are a dangerous opponent who have no fear of reputation or tradition. They are also resilient, as proved by their ability to overcome a 5-0 defeat at Manchester United in the group stage before eliminating Ole Gunnar Solskjaer's side with a 3-2 home win in the final game. Leipzig also defeated Paris Saint-Germain in Group H and have clearly overcome the loss of star striker Timo Werner to Chelsea this summer.

Left-back Angelino is a big threat going forward and his encounter with Trent Alexander-Arnold will be a highlight of the tie, as will centre-half Dayot Upamecano's ability to contain Liverpool's Sadio Mane, Mohamed Salah and Roberto Firmino. Leipzig beat Spurs 4-0 on aggregate at the same stage last season, so they know how to win against English teams, but having conceded 12 goals in six group games, they will give Liverpool chances and that will be the decisive factor in this tie.

Who qualifies?: Liverpool

Porto vs. Juventus

Sergio Conceicao's Porto should not be underestimated in this tie as they displayed their tenacity and ability to frustrate a highly-rated opponent by holding Manchester City to a 0-0 draw in the group stage. They have the experience of Pepe at the back and the goal threat of Moussa Marega and Luis Duaz up front and, while they will be the underdogs against Juventus, Porto will ensure that this tie is close over the 180 minutes.

Juve are desperate to win the Champions League, however, and after a round of 16 exit against Lyon last season, this could be the final shot for this team and Cristiano Ronaldo, who will be 36 in February. Ronaldo scored one of the best goals of his career with a 40-yard strike for Manchester United against Porto at Estadio do Dragao in 2009 and he will want to leave his mark back in Portugal. Juve beat Porto 3-0 over two legs at this stage in 2016-17 and they will need Ronaldo to be fit and firing to ensure that they have a similar result this time around.

Who qualifies?: Juventus

Barcelona vs. Paris Saint-Germain

This is an epic tie and would have been worthy of the final itself, but thanks to the luck of the draw, one Champions League heavyweight will suffer an early elimination which could have huge implications for the coach of the losing side. It is tough to see Barca's Ronald Koeman or PSG coach Thomas Tuchel surviving in their job if they lose this tie. Meanwhile, with ongoing uncertainty over the future of Lionel Messi at Barcelona and Neymar in Paris, this could be the last chance for both players to win the Champions League with their current employers.

Barca are a declining force, as shown in their 8-2 hammering by Bayern last season and, on form, the odds look to favour PSG. The firepower of Neymar and Kylian Mbappe should be too much for Barca's unconvincing defence, but Barca have won their last 13 round-of-16 ties and PSG will still have the scars of their 6-5 aggregate round-of-16 defeat in 2016-17, when they went out despite winning the first-leg 4-0. Four years on, PSG look ready to avenge that humiliation.

Who qualifies?: PSG

Sevilla vs. Borussia Dortmund

This is a tie that pits genuine European trophy-winning experience in Sevilla against a team packed with emerging stars in Dortmund. Julen Lopetegui's Sevilla team displayed their nous and big-game mentality by overcoming Manchester United and Inter Milan to win last season's Europa League -- their sixth Europa League title this century -- but they have never been able to translate their success in that competition into the Champions League.

If they can handle the goal-scoring threat of Erling Haaland and Jadon Sancho, and nullify the star talents of teenagers Gio Reyna and Jude Bellingham, Sevilla will progress, but much also depends on the situation in the coach's position at Dortmund following the sacking of Lucien Favre. Assistant Edin Terzic has taken over in the interim and will hope to keep the upheaval at Dortmund to a minimum as he bids to turn their league form around.

Who qualifies?: Sevilla

Atalanta vs. Real Madrid

Few teams in Europe are as unpredictable as Atalanta and Gian Piero Gasperini's side tend to save their best and worst performances for the Champions League. They reached the quarterfinals last season despite taking just one point from their first four group games and have booked their place in this year's round-of-16 by responding to a 5-0 home defeat by Liverpool with a 2-0 win at Anfield three weeks later.

Real Madrid coach Zinedine Zidane will be concerned about the dangers that lurk for his team against Atalanta, who have the creative force of No. 10 Papu Gomez and goal scoring threat of Duvan Zapata up front. Real made it through with a final-game win at home to Borussia Monchengladbach, so they have to improve quickly or face a third successive elimination at this stage. Atalanta's attacking ability will cause Real problems, but this is a tie that the Spaniards should win. It will be entertaining however it turns out.

Who qualifies?: Real Madrid