A trip to the Etihad has for so long been the stiffest test of all, but City’s defensive frailties were easily exposed and they also badly missed the presence of the injured Erling Haaland in attack.
Liverpool, by contrast, had their talisman fit and firing as Salah took his staggering tally this season to 25 goals and 16 assists in 27 Premier League appearances.
The Egyptian fired the visitors in front on 14 minutes thanks to a brilliantly executed set-piece routine.
Alexis Mac Allister’s corner was flicked by Szoboszlai into Salah’s path and his shot deflected off Nathan Ake past the despairing dive of Ederson.
At the other end, City’s own Egyptian international showed his ability to finish, but Omar Marmoush had strayed offside before being played in by Phil Foden.
City winger Jeremy Doku was skipping past Trent Alexander-Arnold at will, yet the Belgian consistently failed to deliver a telling cross or shot.
Salah was not so forgiving as he raced onto a long ball over the top and teed up Szoboszlai to wrong-foot City goalkeeper Ederson.
The final outcome could have been much more humiliating for City had Liverpool been as accurate on the counter-attack after the break.
Curtis Jones had a third goal ruled out by a VAR review for offside after Szoboszlai just failed to time his run through the heart of the City defence.
Ederson was forced into a stunning save from Luis Diaz and only a brilliant last-ditch tackle from Abdukodir Khusanov denied Szoboszlai a second.
Marmoush scored a hat-trick in last weekend’s 4-0 win over Newcastle and remained a lively threat as he flashed another effort across the front of Alisson Becker’s goal.
But City lacked the end product to make nearly 70% possession count.
Despite an eighth league defeat of the season, Guardiola’s men remain in fourth and will be confident of securing their place in the Champions League next season with a top-five finish likely to be enough.
However, after an unprecedented run of four consecutive titles, City look like yesterday’s team with Liverpool now champions in waiting.
Elsewhere, Newcastle blew Nottingham Forest away with four goals in 11 minutes as Alexander Isak’s double inspired a vital 4-3 win in the race to finish in the top four.
Eddie Howe’s side recovered from Callum Hudson-Odoi’s early opener to run riot with a first-half goal spree at St James’ Park.
Lewis Miley bagged Newcastle’s equaliser, sparking an astonishing spell of dominance as Jacob Murphy put the hosts ahead. Isak netted twice in less than two minutes to reach 50 Premier League goals and leave Forest in tatters.
The Sweden striker has 19 league goals this season, taking him level with Manchester City’s Haaland in second place behind Liverpool’s Salah in this season’s scoring chart.
Nikola Milenkovic and Ryan Yates scored for Forest in the second half, but it was too late for an incredible escape act.
After three defeats in their previous four league games, fifth-placed Newcastle are back in the hunt to qualify for next season’s Champions League via a top-four finish.
The Magpies are behind fourth-placed Manchester City on goal difference, with third-placed Forest just three points above them.
Newcastle keeper Nick Pope made his first league start since early December in place of Martin Dubravka.
But Pope was partially at fault as Newcastle gifted Forest the lead in sloppy style after just six minutes
Jacob Murphy lost the ball in his own half as Hudson-Odoi pressured the Newcastle midfielder into conceding possession.
Hudson-Odoi wasn’t closed down quickly enough by Dan Burn and the winger unloaded a powerful low drive that caught Pope out of position as it flashed into the net.
Miley ensured Newcastle’s strong response to that early setback was rewarded in the 23rd minute.
With Forest’s usually rock-solid defence slow to react, Miley had time to control Lewis Hall’s pass inside the penalty area and drill his shot through a sea of legs past unsighted keeper Matz Sels.
Murphy made amends for his earlier mistake to put Howe’s team ahead two minutes after Miley’s equaliser.
Hall’s driving run was the catalyst as the defender took Isak’s return pass and hit a deflected cross that looped over Sels for Murphy to bundle home from virtually on the goal-line.
Newcastle were firing on all cylinders and they struck again in the 33rd minute.
Ola Aina used his arm to block Hall’s cross, conceding a penalty that Isak dispatched past Sels with an audacious lofted effort that left the keeper sprawled on his back as he tried in vain to claw it out.
Forest had no answer to Newcastle’s intensity and it was no surprise when they conceded a fourth just 60 seconds later.
Joe Willock raced unchecked through the Forest midfield and slipped his pass to Isak, whose shot from 12 yards took a deflection on its way past the wrong-footed Sels.
Newcastle eased up in the second half and Milenkovic reduced the deficit in the 63rd minute, flicking Chris Wood’s cross past Pope from close range.
When Yates steered home in the 90th minute, a nervous hush descended on St James’ Park, but Newcastle held on by their fingernails.
