The troubled champions were blown away by Pep Guardiola's side, who became the first team to score four times in a league game away to Liverpool in 12 years.
Jurgen Klopp's side paid the price for a sloppy display as Steven Alzate's second half strike gave struggling Brighton a memorable success at the expense of the injury-hit champions.
The shock result at Old Trafford leaves Pep Guardiola's Manchester City a point clear at the top with a game in hand and looking increasingly hot favourites to win a third title in four years.
Fernandes struck with 12 minutes left at Old Trafford to cap a thrilling clash that left Liverpool searching for answers after another painful defeat.
The Blues have now won just two of their last eight league games to fall to eighth, nine points behind the leaders.
United are two points clear of second placed Manchester City, who have a game in hand, and third placed Leicester.
Leicester were good value for their first win in three league games as they extended their unbeaten run to four matches.
With little over 48 hours rest between the Foxes' 2-2 draw with Manchester United on Saturday and the trip to Selhurst Park, Leicester boss Brendan Rodgers made seven changes with Jamie Vardy and Youri Tielemans among those left on the bench.
United failed to hold out for a record-equalling 11th consecutive away Premier League win as Vardy's movement outfoxed the visitor's defence.
United dropped down to the Europa League, which they won in 2017, after RB Leipzig knocked them out of the Europe's top competition at the group stage.
Four straight wins have taken Spurs to 20 points after nine games, ahead of Liverpool on goal difference, but Frank Lampard's Chelsea are just two points behind them.
Napoli made sure the fans gathered outside to pay their respects to Maradona weren't disappointed by the current team as an Armando Anastasio own goal and a simple Hirving Lozano finish sealed the points.
The champions were without the injured Virgil van Dijk, Joe Gomez, Trent Alexander-Arnold, Jordan Henderson, Thiago Alcantara, Xherdan Shaqiri and Alex Oxlade-Chamberlain, while top scorer Mohamed Salah was absent due to a positive coronavirus test.
With the final international fixtures of the year done and dusted, a gruelling winter schedule of club football awaits for England's top-flight with nine rounds of league matches before 2 January.
A win at the Etihad would have taken the Reds to the summit but the battle between the two dominant powers of recent seasons ended 1-1.
Yazici's goals put Lille, who are unbeaten in all competitions this season, one point ahead of Milan who lost for the first time since football returned from the first coronavirus lockdown.
Brendan Rodgers' side are just one point behind leaders Liverpool after winning five of their first seven games in a top-flight season for the first time in their history.
The 33-year-old former England international converted two penalties and scored one from open play as the 2016 champions came from 1-0 down at the Etihad on Sunday.
