Cold some days and hot the next, Amoroso breathed flames on Thursday night, his first-half hat-trick crowning Dortmund's 4-0 rout of AC Milan in the UEFA Cup semifinal first leg.

The result, and Amoroso's finishing, have all but guaranteed the Germans a place in the May final in Rotterdam.

'Marcio is a world-class player. It is world-class to be able consistently to bring on this sort of performance and that's what I'm working with him on,' Dortmund trainer Matthias Sammer said after the game.

Amoroso, joint top scorer in the Bundesliga, gave a foretaste of what was to come in the previous round against Slovan Liberec.

Returning from suspension brought on by a red card, Amoroso opened the floodgates in Dortmund's home victory -- another 4-0 win.

But on Thursday, the Brazilian revealed his full potential.

WRONG-FOOTED KEEPER

He confidently wrong-footed Milan keeper Christian Abbiati with a half-step in the eighth minute to score his first goal from the penalty spot.

He then turned rings round Martin Laursen, catching the ball and then flicking it over the flat-footed Danish defender to fire in the second.

For his third strike, he dived in at the far post to head home a cross from compatriot Ewerthon.

But did the fiery Brazilian injure himself in his celebrations?

'No, he was just a little winded from the goal,' said Sammer. 'Everything's in order.'

It seems unlikely that Amoroso will be with the Brazilian side at this year's World Cup as others press their claims but, for Dortmund, he is invaluable.

TEAM DISCIPLINE

'It's his unpredictability that impresses,' said defender Christian Woerns, denying that this very quality could jeopardise team discipline.

Milan coach Carlo Ancelotti was also impressed with Amoroso.

'He's a fine attacker as we saw tonight. But we did give him too far much room,' he said.

The 27-year-old striker, previously with Parma, served a reminder to Italian football of what they are missing and also of the potential which they failed to tap.

In fact, Amoroso did not even make the Parma side that won the 1995 UEFA Cup. But he is unlikely to be left out of this season's final, assuming Dortmund complete the formalities next week.

Ancelotti, who was surprised more by his own side's weakness than Dortmund's strength, said Milan had to believe they were still in with a chance, but acknowledged the task was now 'very difficult'.