Cristiano Ronaldo was feted like a rock star on Wednesday as thousands of fans turned up to watch under-fire Portugal train in Campinas, with the side's World Cup hopes hanging in the balance.

Portugal got off to the worst possible start in Brazil with a 4-0 drubbing from Germany that also saw Pepe sent off for a head-butt and Fabio Coentrao sustain a thigh injury that rules him out of the rest of the tournament.

Ballon D'Or winner Ronaldo endured an afternoon to forget at Salvador's Arena Fonte Nova, where he was over-shadowed by Thomas Mueller's hat-trick.

He stormed through the mixed zone after the game, refusing to answer reporters' questions.

But all that was forgiven in the Campinas sunshine as the side arrived for training at the Estadio Moises Lucarelli.

Music blared from loudspeakers and a helicopter whirred overhead as thousands of fans decked out in Brazil and Portugal shirts waited for the arrival of the Real Madrid star.

The Portugal captain eventually emerged from a tunnel onto the pitch with the rest of the squad about 20 minutes late, wearing orange boots and a grey and green training top, sending excitement to fever pitch.

As he jogged around the stadium, hordes of teenage girls screamed his name and fans pressed their faces against the wire fence to get a closer look at their hero.

Ronaldo, who won the Champions League with Real Madrid last month, came into the tournament on the back of knee and thigh injuries but Portugal coach Paulo Bento confirmed he was doing well physically after the Germany game.

Portugal cannot afford another slip-up when they meet the United States in Manaus on Sunday.

The USA beat Ghana 2-1 in their first match in Group G -- dubbed the group of death -- and are on three points alongside Germany.

The final matches in the group are on June 26, when Portugal play Ghana in Brasilia and the United States meet Germany in Recife.