Just when Jürgen Klopp thought that things could not get any worse for his Liverpool team and, especially, here on the south coast. When they were last at Brighton two weeks ago, the 3-0 Premier League defeat was, to paraphrase the manager, a historic low. Klopp could not remember a worst performance, Liverpool’s traumatic season suffering one of its deepest cuts.

It was a big reason why this FA Cup tie mattered so much. And yet from a position of strength, a goal to the good through Harvey Elliott, they were reeled in by a Brighton team that are attracting fresh superlatives from week to week.

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Lewis Dunk scored to make it 1-1 before half-time and it was Brighton who pushed in the final 20 minutes of the second half, sensing vulnerability in a Liverpool team which has been exactly that for much of the season.

It looked as though Liverpool would hang on. Alisson had denied the outstanding Solly March at close quarters, the rebound flying back off the Brighton winger and going wide, while Ibrahima Konaté had threw himself into a block to keep out Evan Ferguson.

Liverpool got away with a few, not least a challenge from Konaté on Alexis Mac Allister that looked like a last-man foul. Konaté was already on a booking, having gone through the back of Ferguson. Fabinho, on as a substitute, did likewise to the 18-year-old striker, who was forced off in obvious distress – he would leave the stadium on crutches; Fabinho was lucky to see yellow rather than red – while Andy Robertson was booked for a bad one on Mac Allister in stoppage-time.

How Brighton made him pay. From the free-kick, Pervis Estupiñán – in space beyond the far post – sent the ball back across and, after the substitute, Deniz Undav, had challenged with Robertson, serving to block him off, there was Kaoru Mitoma in further space beyond the other post.

What followed was a blur of technical brilliance, the winger taking it down before slicing inside with a touch on his right foot. Before the ball hit the ground, he had guided it into the far, top corner with the outside of the same boot.

Cue a VAR check for an offside against Estupiñán and, when it was ruled on, the roars might have been heard in Liverpool. Brighton march on. The holders are out.

Did it even count as a shock? Brighton are flying high in sixth in the league, Liverpool languishing in ninth and Roberto De Zerbi’s team were portrayed as the pre-match favourites in some quarters. That probably talked to what had happened the last time but it also reflected the broader trajectories of both clubs, with Brighton’s alchemy nothing short of extraordinary.

Since the start of the season, they have lost their manager and most of the coaching staff, important recruitment personnel, their biggest-name defender, main midfielder, top scorer and a key creator. It looks as though their latest star midfielder is on his way, too; there was no sign of Moisés Caicedo, as expected, as Arsenal and Chelsea circle. And they have improved.

The strange thing was that while Klopp talked up how much better Liverpool had been when compared to the previous visit, highlighting the contribution of Cody Gakpo, who had a couple of eye-catching bursts in the No 9 role, De Zerbi felt that Brighton were not at their best.

Liverpool led when Naby Keïta released Mohamed Salah on the counter and he played in Elliott, who had bent his run nicely. The finish found the far corner via the fingertips of Jason Steele. Salah had gone close early on, seeing one shot blocked by Adam Webster and the rebound cleared off the line by Dunk. Salah also dragged wide on 25 minutes after Elliott’s through-ball.

Brighton played some slick and incisive stuff in the first half and they might have led early on. Tariq Lamptey and Estupiñán were under orders to bomb forward from the full-back positions and, with Danny Welbeck up front alongside Ferguson, it was a bold, can-do approach from De Zerbi. Ferguson took some punishment but he emerged with honours.

March, who is in the form of his life, crossed low from the right and, after Welbeck had failed to convert, Ferguson spun and shot. Trent Alexander-Arnold was on the line to clear. Mitoma, so impressive on the other flank, also went close after swapping passes with Ferguson.

Brighton’s equaliser followed a low Lamptey blast after Alexander-Arnold had only half-cleared a corner. It was going wide until Dunk touched instinctively towards goal, wrong-footing Alisson. Lamptey was all action and it was his saving tackle that kept out Elliott just before half-time.

Klopp watched Dunk wobble a free-kick wide after the restart and Pascal Gross lift high. The Liverpool manager made changes, Salah and Gakpo flickered, and yet it would be Brighton who came on strong when it mattered.