Mohamed Salah scored a sublime hat-trick as Liverpool thrashed Manchester United 5-0 to keep pace with the Premier League leaders and pile huge pressure on Ole Gunnar Solskjaer.
The Reds surged to a 4-0 lead at half-time thanks to early strikes from Naby Keita and Diogo Jota before Salah continued his phenomenal scoring run.
Keita cooly finished past David de Gea from Salah's pass before Jota latched onto Trent Alexander-Arnold's cross to double the lead on 13 minutes.
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Salah and Keita then capped another fine team move with the Egyptian finishing from close range before adding his second with a powerful effort moments before the half-time whistle.
The phenomenal Liverpool forward completed his hat-trick in the 50th minute with a dinked finish from Jordan Henderson's wonderful outside-of-the-boot pass.
Cristiano Ronaldo had the ball in the back of the net for United but his consolation goal was ruled out for offside, while Paul Pogba was sent off for a terrible challenge which injured Keita.
This capped a dismal outing for the Red Devils which is sure to raise questions of Solskjaer's future.
Here are six talking points from Old Trafford.
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1. Keita shines before injury
Naby Keita was singled out for criticism after Tuesday's clash with Atletico Madrid despite scoring a brilliant volley in an impressive Champions League victory.
The midfielder was partly at fault for both of Atletico's goals and was taken off at half-time to heighten concerns about his defensive contributions and his place in Jurgen Klopp's plans.
But with Thiago and Fabinho ruled out of the trip to Old Trafford through injury, Keita maintained his spot in the starting XI and took a matter of minutes to reaffirm the many qualities he offers Liverpool.
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Operating as the most-advanced of the midfield trio, the 26-year-old put the Reds ahead with a calm finish from Mohamed Salah's through-ball.
Eight minutes later, he set up Trent Alexander-Arnold to assist Diogo Jota and later grabbed an assist himself for Salah's first goal.
Having endured a goalless 2020/21 season, Keita has already scored three times this campaign and regardless of supposed defensive vulnerabilities, his contributions on the front foot are vital for Liverpool.
It was a major blow to see him stretchered off after Pogba's reckless lunge in the second half.
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2. What went wrong for United?
Well, where to begin.
Manchester United's biggest problem was their inability to coordinate a press while out of possession.
Time and time again their reckless, disorganised closing down handed Liverpool overloads in wide areas; up against players as lethal as Trent Alexander-Arnold, Mohamed Salah and Diogo Jota, United were duly punished.
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Salah in particular was allowed far too much time and space in the box, as shown as he tucked Liverpool's fourth goal into the bottom corner.
The Red Devils were equally shambolic on the front foot, with Bruno Fernandes unusually quiet and Cristiano Ronaldo booked for lashing out at Curtis Jones before his second-half strike was ruled out for offside.
Marcus Rashford also had a poor game after two goals in his previous two appearances and the half-time introduction of Paul Pogba for Mason Greenwood only worsened the situation in a midfield lacking concentration and quality.
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3. Pogba sums up dire Red Devils display
Liverpool's derby delight was marred by the sight of Naby Keita being stretchered off in the second half following a studs-up lunge by Paul Pogba.
As mentioned, the Guinea international was in a fine vein of form but he appears set for a spell on the sidelines as his poor luck with injuries continues.
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Pogba was initially shown a yellow card for his challenge before a VAR check upgraded this to a deserved straight red.
The World Cup winner had only been on the pitch for 15 minutes and his calamitous cameo resulted in him being caught in possession for Liverpool's fifth goal before he was given his marching orders.
Meanwhile, Keita's injury leaves Liverpool light in midfield after James Milner also suffered a muscle complaint and was substituted in the first half, while Jurgen Klopp is also without Thiago and Fabinho.
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4. Klopp's Jota gamble pays off
The release of the team sheets an hour before kick-off brought a number of surprises.
Bruno Fernandes and Marcus Rashford were available to start despite suffering knocks in midweek, while Fabinho missed out for the visitors through injury.
But the decision which caused the biggest stir was Jurgen Klopp's bold call to drop in-form Sadio Mane for Diogo Jota.
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Mane had scored five goals in his previous seven Premier League games, whereas Jota was an unused substitute for last weekend's 5-0 thrashing of Watford.
But the Portuguese got the nod for the trip to Old Trafford and Klopp was vindicated just 13 minutes into the action as he turned in Trent Alexander-Arnold's driven cross.
Jota appears to be a key component of the Liverpool manager's winning formula against United, as he also lined up instead of Mane in the 4-2 victory over the Red Devils last season.
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5. Salah keeps up world-class form
These talking points wouldn't be complete without discussing another three goals and an assist for the player many believe is the world's best at the moment.
Mohamed Salah scored in the 10th consecutive game and his tally for the season is now 15 goals in 12 appearances, with five assists to boot.
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There are not enough superlatives to describe the Egyptian's incredible form this season and with him leading the line, the Reds are poised to push leaders Chelsea and champions Manchester City all the way in the Premier League title race.
A resounding victory in the North-West derby means Liverpool remain just one point behind Thomas Tuchel's Blues.
United, meanwhile, have slumped to seventh in the table with three defeats and a draw in their last four games.
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6. What next for Solskjaer?
There is no shame in losing to a Liverpool side littered with quality from back to front.
But the manner of Manchester United's defeat is sure to prompt a fresh wave of speculation about Ole Gunnar Solskjaer's future as manager.
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The Red Devils have failed to win any of their last four Premier League games and recent Cristiano Ronaldo heroics have only served to paper over the glaring problems at Old Trafford.
A defeat by arch-rivals Liverpool spelled the end of Jose Mourinho's tenure in December 2018, and Sunday evening's humiliation leaves Solskjaer teetering.