Thomas Muller's hat-trick thrust Germany into centre stage in this thrilling World Cup as Joachim Low's side demolished Portugal, their strongest Group G opponents, in Salvador.

Portugal were already 2-0 down before they imploded completely with Pepe, always the man most likely to lose his head, shown a straight red card for a light head-butt on Muller.

Germany, utterly dominant despite playing without a recognised centre forward, went on to win 4-0 with a hat-trick for Muller - the golden boot winner at the last World Cup - and a thunderous header from Mats Hummels.

It meant a hugely disappointing result for world player of the year Cristiano Ronaldo, who had declared himself fully fit from his knee injury.

Portugal face a real test now in a strong group with USA and Ghana where goal difference is likely to prove crucial, and to make matters worse lost another key defender, Fabio Coentrao, to a nasty-looking injury.

Strangely, Portugal had dominated the opening exchanges and Ronaldo inspired the first real chance of note as he played in Hugo Almeida but the moustachioed Portugal striker's effort was weak and easy for Manuel Neuer to claim.

Neuer then came to the rescue again as Ronaldo threatened once more. Miguel Veloso caught Philipp Lahm in possession and with the Portuguese outnumbering the German defence sent Ronaldo racing in on goal but he hammered his shot straight at Neuer from a tight angle.

After that, however, and partly aided by some shocking defending, Germany assumed the early control.

Sami Khedira had already missed a golden opportunity when Portugal keeper Rui Patricio cleared the ball straight to his feet, and though he was 35 yards out the Real Madrid midfielder should have done better with the empty goal beckoning.

That was a let-off for Portugal but Germany were not to be denied.

Joao Pereira pulled back Mario Gotze as he twisted in the box and the Portuguese defender was lucky to be only booked by Serbian referee Milorad Mazic.

Muller did not look for a second as though he would miss the penalty, and he buried it emphatically to put the Germans ahead with 12 minutes gone.

Nani sent a shot skimming over the crossbar as Portugal tried to respond, but it was Germany who struck again.

Gotze had been denied by a last-ditch block after excellent work by Mesut Ozil but from the corner, taken by Toni Kroos, Hummels crashed home a header despite the attentions of two defenders.

Eder headed over from a corner as Portugal tried desperately to get back into the game but then came Pepe's moment of self-destruction.

Muller went down claiming he had been caught in the face by Pepe's arm, but the Real Madrid defender's reaction was to push his head into the German forward's.

It may have been the lightest of head-butts but it was pure stupidity Pepe, who has previous for this kind of thing, and he was given his marching orders.

Muller effectively ended any contest just before the break, firing in off Rui Patricio's body as Portugal's defence gave way again.

Ozil was denied a one-on-one with the keeper, with Muller missing a hat-trick chance with a header from the rebound.

Portugal had a penalty claim of their own turned down after Benedikt Howedes appeared to catch Eder as they challenged for the re-bound from Nani's shot, before Germany finally wrapped it up.

They had made heavy weather of getting the fourth, Gotze in particular being wasteful, but finally Andre Schurrle crossed low and Rui Patricio merely palmed the ball to Muller to poke him from close range with 12 minutes left.

Ronaldo's influence was strictly limited, only a blistering free-kick right at the final whistle and brilliantly saved by Neuer hinted at what might have been.