It felt like springtime at Anfield. The sun came out just before the kick-off to illuminate a wonderfully entertaining match, but it was outshone by the smile on Kenny Dalglish's face as, with his side 3-0 up on their fiercest rivals, he listened to the Kop celebrating his 60th birthday, which fell on Friday.

What Dalglish had seen, as he entered his seventh decade, was the unmistakeable sight of the green shoots of recovery. A club so long mired in doubt and despondency is emerging into the light. After that 1-0 victory over Chelsea four weeks ago, this defeat of Manchester United confirmed the reality of the changes in mood and mentality since the Scot took over in the first week of January.

Dirk Kuyt scored his first Liverpool hat‑trick – and the first goals of his career against Manchester United – but he would have been happy to ascribe the credit for his success to the prodigious efforts of Luis Suárez. The Uruguayan forward, who briefly made himself the most unpopular man in world football last summer by denying Ghana a place in the World Cup semi-finals, has now helped bring a long-lost sense of optimism back to Liverpool.

After Kuyt had struck for the third time, with 25 minutes left on the clock, there were smiles everywhere, but none bigger than on the face of Dalglish. He beamed when he sent on Andy Carroll, his £35m striker, with a quarter of an hour left, when he shook Suárez's hand after withdrawing his goal-maker just before the end of normal time, and when he shared some sort of light-hearted exchange with his captain, Steven Gerrard, during added time.

Liverpool had begun this high-pressure fixture by producing football worthy of a side entirely comfortable with itself. As early as the second minute, interplay between Maxi Rodríguez, Suárez and Raul Meireles almost put Suárez in for an opening goal. While the visitors waited to take measure of the match, Dalglish's men were patiently producing a series of accurate first-time passing moves that dictated the overall shape and rhythm of the exchanges.

Suárez should have been booked by Phil Dowd, rather than merely warned, for the volley of invective loosed at one of the linesmen for failing, in the Uruguayan's view, to spot a foul by Patrice Evra just before the half-hour, but the first of his decisive contributions to the afternoon was not far away.

Anfield has been waiting a long time to see the sort of confidence he showed in broken play following the failure of the United defence to clear a corner from the right, when he set off on a twisting, jinking little dribble which took him past Rafael da Silva, Michael Carrick and Wes Brown before he prodded the ball across the goalmouth, seeing it take a slight deflection off Evra on the way to Kuyt, who tucked it away.

A handful of minutes later it was Suárez's chip from the right that induced Nani to produce the most bizarre of defensive headers, directing the ball back into his own goalmouth for the grateful Kuyt to nod home. The third goal, after 65 minutes, came from Suárez's 20-yard free-kick, which squirmed out of Van der Sar's arms and into the path of the voracious Dutchman, who completed a hat-trick that came from an aggregate range of no more than seven yards.

It would be no surprise were Dalglish to see a little of his younger self in Suárez. At 5ft 11in, the £24m capture from Ajax is three inches taller than his manager, but he possesses a similar talent for using strength and a low centre of gravity to turn his marker and a familiar awareness of the movement of his team-mates. United's spatchcocked defence will not be the only one to suffer.

Kuyt was a deserving beneficiary. No player has worked harder through Liverpool's barren time, in whatever role he has been asked to fill.

This performance was also that of a natural predator, demonstrating the virtues of instinctive movement, lightning reflexes and economical finishing. "I scored more or these kinds of goals in Holland, when I played as a striker," he said afterwards.

The introduction of Carroll provided a further warning to their future opponents that Liverpool, who so recently looked impoverished, now have impressive resources. Cheered when he came on to warm up with his fellow substitutes half an hour before the kick-off, when he stripped off and replaced Meireles, and when his first touch turned out to be a 20-yard header from Jamie Carragher's free-kick, calmly plucked out of the air by Van der Sar, the Geordie appears to embody a new spirit of hope among the faithful.

In Liverpool's hour of triumph, however, a thought had to be spared for poor Ryan Giggs. The great man celebrated the 20th anniversary of his Premier League debut at Stamford Bridge on Tuesday, but left with the taste of defeat in his mouth. He arrived at Anfield to break Sir Bobby Charlton's club record of 606 league appearances, only for United to lose again, with the ground in carnival mood minutes before the final whistle.

Giggs provided the cross from which Javier Hernández scored a consolation goal, but he and Paul Scholes, his fellow veteran, found events wrested from their control by a side whose rejuvenation is now a matter of fact.