Neymar's exit from the World Cup due to a back injury left Brazilians shocked and angered on Friday, darkening the mood after the host's 2-1 win over Colombia in the quarterfinals sparked nationwide celebrations.

The loss of its star player has dented Brazil's chances of winning a record-extending sixth World Cup, and first on home soil, and left Brazilians wondering who can replace the mercurial striker for Tuesday's semifinal showdown with Germany.

"Neymar fractures vertebra and is out of the Cup," the country's three main newspapers headlined in their online editions, completely overshadowing accounts of the thrilling victory.

The papers published blow-by-blow diagrams of the play in which Neymar was kneed in the back by Colombian defender Juan Zuniga, burying coverage of the stunning free kick by David Luiz that sealed the win.

"This is terrible news ... the worst possible news. Neymar is so important to us," said student Fabian Ruiz, 19, walking with friends down a street in Belo Horizonte, dressed in Brazil's trademark canary yellow shirts and quaffing beer from cans.

"Without him, the other players will have to fight more. It is going to be so difficult against Germany now."

A large crowd of fans wearing Brazil shirts gathered outside the hotel in Fortaleza where Neymar was taken after the match.

As he was being taken in on a stretcher, they chanted: "Forza Neymar!" ("Be strong Neymar!")

Social media was flooded with messages about the incident, with many Brazilians calling on world soccer's governing body FIFA to punish Zuniga in the same way Uruguay striker Luis Suarez was penalized for biting an Italian player.

One columnist went so far as to describe the challenge as a "savage attack."

"Neymar out of the Cup because of cowardice and foul play by the Colombian player," Fabricio Tavares, a Brazilian university professor, wrote on Facebook, echoing a common view heard on streets and in bars around Brazil.

Wishes for a speedy recovery poured in from all over, including Argentine playmaker Lionel Messi, Neymar's teammate at Barcelona.

Even Brazilian President Dilma Rousseff used her Twitter account to call on Brazilians to unite around Neymar and the national team.

Argentine soccer great Diego Maradona also lamented Neymar's injury, telling Venezuela-based Telesur TV network: "It concerns not only the Brazilian people but all of us who love football.

"It was his World Cup, in his country. He had great hopes."

At a bar in Sao Paulo, couples were still dancing late on Friday night to celebrate the win over Colombia, but the news of Neymar's injury dampened the mood.

"We were so happy but now it is sad. Very sad," said Monica Ferreira, 27, who watched the game at the bar with friends.

"He is our best player. We love him because he plays so hard when he puts on the Brazil shirt."

Some fans thought Brazil's chances were over without Neymar.

"He is our best player. I don't think we can win the Cup without him," said a distraught-looking Eduardo Gomes, a 33-year-old fan, as he texted to find out more about Neymar's injury.

SHARPSHOOTER LUIZ SAYS IT'S ALL IN THE GENES

David Luiz can only explain the technique behind his game-clinching free kick in the World Cup quarterfinal win over Colombia as a product of genetics.

Lining up from 35 meters, the 27-year-old Brazilian side-footed the ball with his right boot, smashing it over a wall of four Colombians and beyond the reach of goalkeeper David Ospina.

It gave Brazil a 2-0 lead in the 69th minute, and the tournament host held on to win 2-1 to reach the semifinals.

Asked about it later, Luiz gestured with his hands out diagonally in different directions and joked that it represented how his feet were when he was little.

"I think it's genetic; I was born with legs like that," Luiz said, spreading his hands apart like two feet sticking out toward opposite sides. "In Brazil, they call it '10 to 2'."

Luiz celebrated the goal by leaping over the corner flag to greet the noisy Brazil fans who packed Arena Castelao.

He acknowledged it would be almost impossible to repeat the free kick.

"Today it was great because I hit the ball at the exact (right) point," he said "You can (try) to hit it like that and it'll take you all day. I am so happy because I can help my team with this.

Brazil coach Luiz Felipe Scolari said Luiz had been studying free-kick videos leading up to the Friday's match, concentrating on the technique used by a now-retired specialist at a Brazilian club.

"I think he watched many videos," Scolari said. "We had a player who played in Corinthians, Marcelinho Carioca. He used to kick like that like no one else."