Champions League title-holders Bayern Munich return to European action on Tuesday for the start of the knockout stage.

Liverpool, Paris St Germain and Borussia Dortmund gained victories on the road last week and several other heavyweights will resume their campaign with round-of-16 ties in the coming days.

Here, the PA news agency looks at the key talking points before the four matches to be played on Tuesday and Wednesday.

Can Bayern go back to back?

Bayern Munich were virtually untouchable in 2020 but have endured a tricky start to the new year and will not want to jeopardise the defence of their Champions League title this week with another below-par showing in Rome. Eintracht Frankfurt inflicted a 2-1 defeat on Hansi Flick’s side this past Saturday to add to a shock DFB-Pokal second-round exit last month and their 3-2 loss to Borussia Monchengladbach on 8 January. Further problems at Lazio and a full-blown crisis will be under way.

Immobile vs Lewandowski

Two of the best goalscorers in Europe will face off at the Stadio Olimpico. While Robert Lewandowski finished with the most goals in the 2019-20 Champions League, he was pipped overall by Ciro Immobile. The Italian found the net on 36 occasions for Lazio in Serie A, the most of any player in Europe’s top-five leagues. Bayern ace Lewandowski was only two off that tally but will be out to show who is top dog during Tuesday’s round-of-16 first leg. Lazio’s No 17 has not rested on his laurels, though, and has 19 goals already this term.

Suarez faces his old foes again

There is no love lost between Luis Suarez and the Chelsea fans. It was back in 2013 the Uruguayan received a 10-match ban for a bite on Branislav Ivanovic at Anfield. It has not been forgotten by the Blues faithful but the former Liverpool striker does not boast the best of records against the Premier League side. He has scored only twice in nine appearances but with eight already to his name in 2021 with Atletico Madrid, the 34-year-old will be out to improve that during this two-legged tie.

Is this City’s year?

Manchester City have been a domestic force for more than a decade but success in Europe continues to elude them. It has been a similar story for Pep Guardiola, who failed to lead Bayern to Champions League glory and has not won the trophy since 2011 with Barcelona. There have been close shaves but could 2021 be the year the cup returns to Manchester? On an 18-match winning streak, the Citizens will not fear Monchengladbach and with a perfect balance between defence and attack, they look favourites for a reason.

Madrid out to avoid unwanted hat-trick

Real Madrid are the most successful team in the competition with 22 wins and claimed three in a row between 2016 and 2018. However, since that success over Liverpool three years ago, Los Blancos have failed to make it past the round of 16. Ajax and Man City have proved too strong at this stage during the past two campaigns and in Atalanta this time, Zinedine Zidane will know they are facing an up-and-coming outfit. The Italians won at Anfield in November and were within touching distance of the quarter-finals last year.