The Champions League returns later this week to complete the last-16 second leg ties before the whole competition heads to Lisbon for the final rounds.

Here the PA news agency looks at some of the issues as the matches restart.

Good omens for City?

Manchester City have failed to get beyond the quarter-finals the last couple of seasons and have only reached the last four once, in 2015-16. But beating UEFA with a successful appeal to the Court of Arbitration for Sport against their two-year Champions League ban may be a good omen. They are joint-favourites with Bayern Munich to win it for the first time and have already lifted the League Cup this season. They are set to be without Sergio Aguero as they seek to consolidate their 2-1 lead over Real Madrid but Pep Guardiola's free-scoring side have more than enough firepower to get to the final.

Time for Ronaldo to step up

Juventus last won the Champions League in 1996 and have been runners-up five times since. With a ninth successive Serie A title comfortably secured with two matches to go they immediately turned their attention to overturning the 1-0 deficit to Lyon. The competition's all-time leading goalscorer Cristiano Ronaldo has scored just twice in seven appearances but 10 in his last 11 matches domestically suggest he has lost none of his sharpness and Juve need him to come alive in the latter stages if they are to end their long wait.

Chelsea look to Liverpool for inspiration

Last season Liverpool produced a brilliant comeback at Anfield to overturn a 3-0 deficit and beat Barcelona 4-3 in the semi-final on their way to winning the trophy. Chelsea face a similar prospect but away against a Bayern Munich side who are much more robust and the odds are stacked against them even more. Frank Lampard's squad has a growing list of injuries and the weekend's FA Cup final defeat will not have helped morale. Olivier Giroud has scored six goals in eight matches but is going to need assistance from somewhere and with Christian Pulisic and Pedro injured it is a tall ask. As is stopping Robert Lewandowski, the competition's leading scorer with 11, and conceding one goal will probably signal the end of Chelsea's hopes.

Will surprise packages continue to astound?

Atalanta and RB Leipzig are both in the quarter-finals for the first time, the Italian side impressively in their first appearance in the competition. Buoyed by the highest league finish in their history Atalanta have the potential to shock Paris St Germain, who have a reputation for struggling in the big games having never got past the quarter-finals. The French club could be without mercurial forward Kylian Mbappe and with Atalanta playing with freedom there could be more pain to come for the Parisians. Leipzig are also relative novices, although not newcomers, and the last eight is new territory for them. Losing Timo Werner to Chelsea is a blow to their hopes of progress and Atletico Madrid look a much tougher prospect without him.

Messi redemption?

Barcelona's Argentinian forward Lionel Messi cut a desolate figure after the defeat at Anfield last season and admits that collapse still haunts him. Barca, who lost the league title to arch-rivals Real Madrid, need some good news to finish the season and Messi is the man to deliver it if he can exorcise the demons of Anfield, starting against Napoli at home with the tie slightly in their favour with an away goal at 1-1.