The right-back went down holding his leg off the ball midway through the second half, and received treatment on the pitch before being replaced by James Milner.
Jurgen Klopp confirmed in his post-match press conference that Alexander-Arnold would miss England’s fixtures with Ireland, Belgium and Iceland during the international break, and a scan revealed the extent of the injury on Monday.
The news hasn’t improved Klopp’s dim view of the decision to return to three substitutes per game in the Premier League, after the switch to five post-lockdown.
The German was outspoken in his criticism of Premier League CEO Richard Masters after the City game, saying Alexander-Arnold would not be the last player to suffer from the heavy workload this season.
While Milner was the obvious replacement off the bench at the Etihad, Alexander-Arnold’s absence could present a first-team opportunity to Neco Williams.
The 19-year-old has made four first-team appearances for the Reds so far this season, most recently coming on as a late substitute to make his Champions League debut in the 5-0 win over Atalanta.
He also started in the Community Shield against Arsenal and played 90 minutes in Liverpool’s Carabao Cup games against Lincoln and Arsenal.
Liverpool are, of course, already without defensive lynchpin Virgil van Dijk and his initial replacement Fabinho.
Georginio Wijnaldum said on Monday that Van Dijk is ‘going through hell’ with his long-term knee injury, but backed him to recover in time to join him at Euro 2020 with the Netherlands.
The news of Alexander-Arnold’s absence at Liverpool will be softened by the fact it is now the international break, but it presents a new headache for England boss Gareth Southgate.
The Three Lions are at least well stocked at right-back with Kyle Walker, Kieran Trippier and Reece James all called up in the initial 29-man squad.