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Curtis Jones scored the only goal after an error from Ajax keeper Andre Onana.
The FA has been in contact following the incident that sees Cavani facing a potential three-game ban.
Porto boss Conceicao accused Guardiola and has backroom staff of attempting to influence officials.
City have made a mixed start in the Premier League, winning just three of their opening eight games and finding the net only 10 times.
Manchester City advanced through their group for an eighth successive year.
Josip Ilicic and Robin Gosens netted for the Italian side.
Lampard stressed that the 20-year-old’s so-far limited amount of first-team action does not mean he is out of favour.
The striker scored the winning goal in the 2-1 victory at Rennes.
The Red Devils got back on track in the Champions League by beating Istanbul Basaksehir at an empty Old Trafford on Tuesday evening.
The Serie A side arrive at Anfield looking to avenge their heaviest home European defeat courtesy mainly of a Diogo Jota hat-trick three weeks ago.
Antoine Griezmann was also on target as Ronald Koeman’s side made it four wins from four.
The Portugal playmaker scored twice, with Marcus Rashford and Daniel James also on target in a 4-1 win.
Callum Hudson-Odoi had scored the Blues’ opener in a 2-1 win at Rennes
The Argentina striker missed the end of last season and the start of the current campaign after undergoing knee surgery in June.
The France striker has played just 36 minutes in the Premier League so far this season.
Wales face a group decider against Finland on Wednesday.
The Old Trafford boss deflected questions over his position following the 2-1 loss.
Tammy Abraham added a third for the Blues.
Former Premier League striker Demba Ba scored as Istanbul Basaksehir won 2-1.
The Brazil striker netted decisively in the Champions League victory against Olympiacos.
Lior Refaelov scored the only goal in the first half.
The Foxes remain joint top of Group G in the Europa League.
The proposition would involve the elite teams from the continent.
Mason Greenwood and Anthony Martial were also on target.
The Juventus star contracted Covid-19 while on international duty with Portugal.
The hosts deployed a five-man back line in the hope of absorbing pressure and hitting City on the break.
The makeshift central defender went off in the 2-0 home win over Midtjylland.
Ferran Torres, Ilkay Gundogan and Raheem Sterling on target in 3-0 success.
Pep Guardiola will be without five first-team players in Marseille, with another two just returning from injury.