Manchester United answered Sir Alex Ferguson's wake-up call in scintillating style as they powered past Fiorentina into the Champions' League quarter-finals.

Before the game Ferguson had told his players that the challenge had arrived and that it was time for them to rise to it.

The United boss had become worried by a succession of spluttering displays at a time when his finely-tuned side is usually hitting top gear.

But, as so often is the case with his Treble winners, they delivered when it mattered most and this was arguably their finest display of the season.

This was more like the United of last season as they ruthlessly took Fiorentina apart and this was a performance worthy of the mantle of European champions.

Andy Cole, with his record-equalling 14th Champions' League goal, Roy Keane and Dwight Yorke netted for United, but it would be wrong to single out individuals for praise on a night when the whole team shone.

Victory swept United into the last eight, with a Group B game to spare, for the fourth successive season and sets up the possibility of an all-Premiership clash with Chelsea in the next round.

The result also earns the football billionaires £1.54million on top of the £3.75m they have already made from tournament.

But that will be the last thing on Ferguson's mind and he will be delighted to see his side back to their best.

For the second successive European game at Old Trafford, kick-off was delayed.

Two weeks ago there was a 45-minute delay because of an accident on the nearby M60 and this time there was a 15-minute wait caused by a partial power failure.

Perhaps it was all a cunning ploy by Ferguson to get the crowd pumped up because when the teams emerged, the fans answered his plea to make themselves heard.

When the game eventually got underway, Henning Berg was given the chance to atone for his blunder against Fiorentina in November's 2-0 defeat and he made his first European start since that fateful night.

The Norwegian retained his place as the error-prone Mickael Silvestre was dropped for the first time in his six-month United career to make way for Jaap Stam.

Silvestre the cat had finally run out of lives.

Gabriel Batistuta was another player who had not been on top form in recent weeks.

The one-time United target had not scored for over a month and his plight has not been helped by tendon problems in his ankles.

However, Batistuta looked as sharp as ever when he let fly from 25 yards with a drive which whizzed past Mark Bosnich's near post.

Fiorentina, who are only eighth in Serie A, went close again when Bosnich made a fine double save from Rui Costa.

Back came United and Francesco Toldo saved from Cole before Jorg Heinrich made a great saving tackle on Yorke as he shaped up to hit home the rebound.

Fabio Rossitto then made a great defensive header to touch Cole's cross off the head of David Beckham before Toldo parried a fiercely-hit Keane effort.

United did not heed Batistuta's warning shot and on 16 minutes the Argentinian hitman fired home from 25 yards out with a thunderous shot, which flew past a stunned Bosnich.

Four minutes later United were back on level terms thanks to Cole's 20th strike of the season.

Gary Neville crossed to Cole on the edge of the area and he turned Tomas Repka before hitting a right-foot shot into the bottom corner of the net.

The strike took him level with Denis Law as United's leading scorer in the competition, although the Scot bagged his 14 goals in almost half as many games as Cole.

After months of mediocre fare, the United fans were at last being served up a real treat of a match.

Chances continued to be created at both ends and Bosnich grabbed a near-post header from Batistuta before Toldo tipped Cole's attempted chip over the bar.

It seemed inevitable that another goal would come and it did on 32 minutes through United's top scorer in Europe this season, Keane.

Berg headed against the crossbar from Beckham's deep corner and the United skipper rifled home the rebound for his sixth Champions League goal of the campaign.

Beckham then picked up his third booking, which rules him out of the Valencia game on Tuesday, for a foul on Heinrich, but that hardly matters after this result.

The pair carried on their private battle and after some tugging and pushing, Beckham threw himself to the ground claiming a foul, but referee Ryszard Wojcik gave nothing.

Ryan Giggs revels in matches against Italians and this was no exception and from one mazy run five minutes after half-time, he meandered past two despairing Fiorentina challenges before shooting over.

The Welshman went close again when he connected with Beckham's cross only to see his header deflected for a corner.

Despite United's domination, Batistuta remained a threat and he directed a free header wide from six yards out.

But Fiorentina's hopes of an equaliser vanished when Rossitto was sent off in the 61st minute for a cynical foul on Yorke midway inside his own half.

Yorke exacted his own retribution when he headed home Giggs' cross for United's third of the evening on 70 minutes to seal victory.

Teams:

Man Utd: Bosnich, G. Neville, Berg, Stam, Irwin, Beckham, Keane, Scholes, Giggs, Yorke, Cole.

Subs Not Used: Van Der Gouw, Butt, Sheringham, P. Neville, Solskjaer, Fortune, Silvestre.

Booked: Beckham.

Goals: Cole 20, Keane 32, Yorke 70.

Fiorentina: Toldo, Repka, Adani, Pierlini, Torricelli (Tarozzi 75), Di Livio (Amoroso 75), Rossitto, Rui Costa, Heinrich, Batistuta, Mijatovic (Chiesa 62).

Subs Not Used: Taglialatela, Fircano, Okon, Bressan.

Sent Off: Rossitto (61).

Booked: Torricelli, Adani, Pierlini.

Goals: Batistuta 16.

Att: 59,926

Ref: Ryszard Wojcik (Poland).