There are the good Anfield European nights, there are the great ones and then, like this one, there are those remarkable occasions which fall into a different category altogether. This morning Liverpool awake to contemplate the prospect of a third Champions League semi-final against Chelsea in four years, although how they got there is a story that will outlive whatever else happens this season.
It is that man again. In the final 21 minutes of last night's game, Rafael Benitez made a crucial substitution, watched his side win the tie, then lose it and then win it all over again. In his precise, meticulous world it was perhaps not how the Liverpool manager planned it but it certainly made for an absorbing, compelling spectacle. How does such a control freak of a man conspire to preside over so much joyously chaotic football?
The Liverpool heroes changed as rapidly as the destiny of the tie which itself switched five times. First of all it was Fernando Torres, scorer of Liverpool's second goal which put them 2-1 in the lead; then Steven Gerrard who converted the penalty that made it 3-2, and finally Ryan Babel, scorer of the fourth and the man who won the penalty. But it was Benitez who made the changes that mattered, who gambled with his formation and who has had the edge over Arsène Wenger in both ties.
Poor old Wenger – left to scoop up the remains of Arsenal's season like the shattered pieces of a priceless vase. It was sad that it should end like this with him railing against the award of that crucial penalty to Babel for the admittedly soft challenge of Kolo Touré, but even Wenger must have recognised that a side as forceful and relentless as Benitez's would find the fragile heart of Arsenal sooner or later. Yet amid the wreckage of Arsenal's night one astonishing memory will stand out.
That was the run of Theo Walcott, half the length of the pitch and past the challenges of four Liverpool players to lay Arsenal's second goal on a plate for Adebayor on 84 minutes. It was a moment that made Anfield gasp, a run of staggering confidence and jaw-dropping pace. And despite all the misery that will surely accompany another season without trophies for Arsenal it is the timely signal that the 19-year-old Englishman is ready to start matches like these rather than be thrown on at the end to rescue the game.
Had the story ended there for Liverpool we would be talking only of Walcott this morning. But he was upstaged by another young prospect, Babel, whose influence was decisive. So now the mind turns to 23 April when Avram Grant tries to accomplish what his predecessor Jose Mourinho never achieved in two attempts against Benitez – win a Champions League semi-final. If Grant wants his stripes as a manager then there is no better tie to win than the one that Mourinho failed in twice.
These days, Champions League away games at Anfield must feel about as welcoming for opposition managers as an unaccompanied stroll through the lions' enclosure at Knowsley safari park. Even Wenger was the subject of an ambush last night, a radically new 4-4-2 Liverpool formation with Peter Crouch in attack alongside Torres and Gerrard moved out to the unfamiliar left wing. In that position, the Liverpool captain seemed to be sulking for long periods of the game but even when sulking he can still conjure up a match-winning performance.
Take a deep breath and consider how the tale unfolded. Abou Diaby's goal on 13 minutes was beautifully worked, Cesc Fabregas controlling the ball on the edge of the area, passing to Alex Hleb once, then again. He rolled an angled pass into the right channel of Liverpool's area and Diaby darted in to beat Reina at his near post. It had started as a move long before when Touré won the ball from Gerrard.
It could have been the moment that Arsenal's season finally rekindled itself but they were dragged back so simply. The first decent cross into their area, a corner from Gerrard on 30 minutes and Sami Hyypia equalised with a fierce header when Philippe Senderos should have been marking him at the back of the area. It was not the last time the Swiss defender was to find himself culpable.
On 42 minutes a low-key but significant moment, Mathieu Flamini carried off on a stretcher with an ankle injury. Just as Marco Materazzi was dismissed against Liverpool in the first leg against Internazionale this seemed like a fortuitous moment for the home side. A crucial player for Arsenal was removed and replaced with Gilberto Silva who, these days, is not the effective force he once was.
It is the tiny margins that make the difference, the moments that change the course of a season. Liverpool never threatened to run riot against Arsenal but the pressure was unrelenting and then, on 69 minutes, came the breakthrough. It started with a long ball forward and a touch down from Crouch's head to the right foot of Torres. This time Senderos had given the Spanish striker a yard of space – it may as well have been 10. Two touches with that brilliant right foot and the third dispatched his 29th goal of the season into the roof of Almunia's net.
The game bloomed. On came Walcott and Robin van Persie. From Hleb's cross from the left, Adebayor guided his shot wide of the post. Babel replaced Crouch and Arsenal stretched Liverpool, never abandoning their football for the direct approach. Walcott must have thought his moment had arrived. His run in the 84th minute was incredible, leaving in his wake Xabi Alonso, Fabio Aurelio, Javier Mascherano and Hyypia. He cruised into the Liverpool area and squared the ball to Adebayor who made the score 2-2.
Then the final act. The penalty won by Babel was undoubtedly soft, the merest of tugs from Touré bringing the Dutchman down. In front of the Kop, Gerrard swept the penalty past Almunia. Then the crescendo: a hoof forward by Dirk Kuyt and Babel out-sprinted the last covering man Fabregas to slip the ball past Almunia. At 4-2, Anfield could say that, yes, this brilliant game was over and they had won although how they got there was still hard to fathom.
Liverpool (4-4-1-1): Reina; Carragher, Skrtel, Hyypia, Aurelio; Kuyt (Arbeloa, 90), Alonso, Mascherano, Gerrard; Crouch (Babel, 77); Torres (Riise, 87). Substitutes not used: Itandje (gk), Voronin, Benayoun, Lucas.
Arsenal (4-4-1-1): Almunia; Touré, Gallas, Senderos, Clichy; Eboué (Walcott, 72), Flamini (Gilberto, 42), Fabregas, Diaby (Van Persie, 72); Hleb; Adebayor. Substitutes not used: Lehmann (gk), Song, Bendtner, Hoyte.
Referee: P Frojdfeldt (Sweden).
FIRST LEGS - Tues 22/Wed 23 April
Liverpool v Chelsea
Schalke 04 or Barcelona v Roma or Manchester United
SECOND LEGS - Tues 29/Wed 30 April
Chelsea v Liverpool
Roma or Manchester United v Schalke 04 or Barcelona
Wednesday 21 May (Moscow)