Sadio Mané could join an elite group when Liverpool play Porto, while Tottenham face the weight of history as they travel to the Etihad with a 1-0 lead.
Liverpool and Manchester City are doing battle for the Premier League title and both sides also remain in the hunt for the Champions League.
The Reds face Porto on Wednesday, holding a 2-0 advantage from the first leg, and Jürgen Klopp will be hoping for a repeat of their rampant 5-0 victory at Estádio do Dragão in last season's round of 16 - a game in which Sadio Mané starred.
City, meanwhile, host Tottenham, with Pep Guardiola's side having to comeback from a 1-0 deficit, though Mauricio Pochettino will have to do without Harry Kane, who was injured in the first leg.
Here are some essential Opta Facts as we close in on the business end of the competition.
Porto v Liverpool
3 - Mané scored a hat-trick for Liverpool versus Porto last term. Only Luiz Adriano versus BATE and Cristiano Ronaldo against Atletico Madrid have recorded more than one hat-trick against an opponent in the Champions League, while no player has got two away to one club.
7 - Liverpool have never lost a European match against Porto in seven previous encounters, winning four times and drawing on three occasions, keeping three successive clean sheets in the process.
9 - The Reds have progressed from all nine of their previous two-legged European ties under Jürgen Klopp (four in the 2015-16 Europa League, one 2017-18 Champions League play-off and four knockout stage fixtures in the same competition).
2 - Two of the three teams that lost their first leg by two or more goals in the last 16 of this season's competition managed to turn the tie around in the return fixture; Manchester United v Paris Saint-Germain and Juventus v Atlético.
100 - Porto are the only remaining side in the Champions League to have won all of their home games in the competition this season.
5 - Liverpool's 5-0 win in last season's meeting at Estadio do Dragao was Porto's heaviest defeat in European competition.
Manchester City v Tottenham
4 - Tottenham have won three successive Champions League games; they have never been victorious in four in a row.
23 - City have won 23 of their 25 home matches in all competitions this season (L2), although they have suffered defeat in two of their past three Champions League knockout games at the Etihad Stadium, winning the other 7-0 against Schalke.
93 - Each of Tottenham's past 10 goals in the Champions League have come in the second half; indeed, 93 per cent of their goals (13/14) in the competition this season have been netted after half-time.
7 - Leroy Sané has been directly involved in seven goals in his last three home games in the Champions League (three goals, four assists). It is four more than he managed in the previous seven such outings at the Etihad.
8 - The first leg saw eight different English players in the two starting XIs. The last Champions League fixture to feature more Englishmen in the line-ups was the 2008 final between United and Chelsea.
1 - Tottenham have only won one of their last eight visits to City in all competitions, a 2-1 Premier League victory in February 2016.