Liverpool led after five minutes, when Salah set up Naby Keïta to score. Diogo Jota made it 2-0 eight minutes later, turning in Trent Alexander-Arnold’s cross.
Salah then took over. He scored from Keïta’s pass in the 38th minute and added another from Jota’s pass in first-half stoppage time. It was the first time United had been 4-0 down at half-time in Premier League history.
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Ole Gunnar Solskjær brought on Paul Pogba for Mason Greenwood at half-time, but Liverpool scored again within five minutes of the restart. Jordan Henderson played Salah through, and the Egyptian finished calmly to complete his hat-trick.
Things got worse for United on the hour. Pogba was shown a red card for a high challenge on Keïta, which was upgraded from a yellow after a VAR review. Keïta was carried off on a stretcher.
It was Liverpool’s biggest win at Old Trafford and, according to AFP, their biggest win over United at any ground since 1925. It also followed a 5-0 win at Watford eight days earlier.
Salah’s hat-trick was the first by an away player at Old Trafford since Brazilian striker Ronaldo scored three for Real Madrid in 2003. He also overtook Didier Drogba as the highest-scoring African player in Premier League history, and he had now scored in 10 games in a row in all competitions.
The win left Liverpool second in the table, one point behind leaders Chelsea.
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Both clubs are at home on Sunday. Liverpool host in-form Brighton at Anfield at 16:00 SAST, while United, without a win in seven games in all competitions, host Bournemouth.
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