Bayern Munich take on Paris Saint-Germain in the Champions League last 16, a heavyweight clash between clubs who faced off in the 2020 final. Here's a look at some of the key match-ups which could determine where the tie is won and lost ahead of Tuesday's first leg:

Christophe Galtier v Julian Nagelsmann

After a strong start domestically, PSG's form has dropped off considerably since the turn of the year and coach Galtier finds himself entering a critical stretch of the season without Kylian Mbappe.

The France star, the joint-leading scorer in this season's Champions League with seven goals, will miss the first leg with a thigh injury and there are concerns over Lionel Messi too after the Argentine hurt his hamstring during Wednesday's 2-1 loss to Marseille in the French Cup.

With Neymar yet to rediscover his best form since the World Cup either, Galtier must devise a plan that will allow a diminished PSG -- whose squad was also hit by a stomach bug at the weekend -- to avoid another European disappointment.

Bayern appeared to have turned the corner after going through what their coach Nagelsmann called a "results crisis" following three straight draws last month.

The 35-year-old Nagelsmann has also been hindered by injuries to key players but the club brought in cover in January and expectations remain as high as ever in Bavaria.

Gianluigi Donnarumma v Yann Sommer

The Italy goalkeeper made a costly error as PSG were dumped out by Real Madrid in the last 16 a year ago but is now entrenched as their first-choice goalkeeper.

PSG twice reached at least the semi-finals with Keylor Navas in goal before the arrival of Donnarumma, whose signing was intended to help the French champions win Europe's biggest club prize.

Bayern have signed Switzerland goalkeeper Yann Sommer as a replacement for Manuel Neuer, who will miss the rest of the season after breaking his leg while skiing in December.

Sommer, 34, has past Champions League experience with Borussia Moenchengladbach and Basel but the scrutiny will be much sharper with the six-time European champions.

Germany trio v Verratti

Bayern figure to have the advantage in midfield with Germany internationals Joshua Kimmich and Leon Goretzka patrolling the central areas and the impressive Jamal Musiala in a more advanced role.

Musiala, not yet 20, is Bayern's leading scorer with 14 goals while there are few midfielders in the world as complete as Goretzka and Kimmich.

However, it is a longstanding area of weakness for PSG, heavily reliant on Marco Verratti, whose fitness is again in question with the Italian receiving treatment for a sore hip.

Fabian Ruiz and Carlos Soler have not settled since arriving in the summer, Vitinha's form has dipped and Renato Sanches is likely ruled out of both legs with a hamstring problem.

Eric-Maxim Choupo Moting v Sergio Ramos

Choupo Moting was on the losing side after coming on late for PSG in the final three years ago, his final appearance in an underwhelming stint in the French capital.

Bayern seemed an unlikely next destination for the Cameroon striker, but his contribution this season for a team coming to terms with the departure of Robert Lewandowski and absence of Sadio Mane cannot be understated.

His 13 goals are second only to Musiala and his ability to occupy defenders affords Bayern's more dynamic attackers like Serge Gnabry and Leroy Sane extra space to do damage.

Ramos was signed to bring extra depth and experience to PSG, but the 36-year-old has played far more regularly than perhaps expected with Presnel Kimpembe sidelined by injury.

Lionel Messi v Dayot Upamecano

Less than two months on from the World Cup final, Dayot Upamecano will again be tasked in part with shutting down Messi -- assuming he plays, as Galtier insists he will.

Seven-time Ballon d'Or winner Messi had the last laugh in Doha with two goals and a helping hand in the other, before converting in the shootout.

Upamecano has started every game for Bayern in the league this term, growing in stature after an up-and-down first season in Bavaria.

PSG's attack is not the same without the blazing speed of Mbappe, but Messi and Neymar can still pose plenty of problems for a Bayern defence reinforced by the recent signing of Joao Cancelo.

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